Mathematical and physical aspects of the applicability of the Onsager, Prigogine as well as the Glansdorff and Ziegler thermodynamic extremal principles (TEPs) to non-equilibrium thermodynamics are ...examined for systems at fixed temperature with respect to their ability to provide kinetic equations approved in materials science. TEPs represent an alternative to the classical phenomenological equations approach. As TEPs are, more or less, a pure mathematical tool, they cannot significantly contribute to a deeper physical understanding. However, if a system can be described by discrete characteristic (thermodynamic) parameters, it is demonstrated that application of Onsager’s TEP or Ziegler’s TEP represents a systematic way to derive a set of explicit evolution equations for these parameters. This approach can significantly simplify the treatment of the problem and, thus, can also be applied to rather complex systems, for which the classical approach, involving application of phenomenological equations, fails. The application of TEPs is demonstrated on plasticity with respect to constitutive equations as well as on grain growth and coarsening with respect to evolution equations of discrete parameters. No exploitation of Prigogine’s TEP has been reported for applications in materials science. Contrarily, Prigogine’s TEP can be invalidated if the coefficients of the dissipation function depend on the evolution of state variables with time. This is demonstrated by a further practical example worked out for the solute drag phenomenon. Glansdorff’s and Prigogine’s evolution criterion, however, is always fulfilled near the equilibrium state of convex Gibbs energy. Extensions of TEPs to non-linear non-equilibrium thermodynamics are demonstrated for homogeneous and quasi-homogeneous dissipation functions.
Background:
There is no consensus on the optimal method of stabilization (arthroscopic or open) in collision athletes with anterior shoulder instability.
Purpose:
To examine the effect of ...“subcritical” bone loss and football-specific exposure on the rate of recurrent shoulder instability after arthroscopic stabilization in an intercollegiate American football population.
Study Design:
Case-control study; Level of evidence, 3.
Methods:
Fifty intercollegiate football players underwent primary arthroscopic stabilization for anterior shoulder instability and returned to football for at least a single season. Preoperatively, 32 patients experienced recurrent subluxations, and 18 patients experienced a single or recurrent dislocation. Shoulders with glenoid bone loss >20%, an engaging Hill-Sachs lesion, an off-track lesion, and concomitant rotator cuff repair were excluded from the study. The primary outcome of interest was the ability to return to football without subsequent instability. Patients were followed for time to a subsequent instability event after return to play using days of exposure to football and total follow-up time after arthroscopic stabilization.
Results:
Fifty consecutive patients returned to American football for a mean 1.5 seasons (range, 1-3) after arthroscopic stabilization. Three of 50 (6%; 95% CI, 1.3%-16.5%) patients experienced recurrent instability. There were no subsequent instability events after a mean 3.2 years of military service. All shoulders with glenoid bone loss >13.5% (n = 3) that underwent arthroscopic stabilization experienced recurrent instability upon returning to sport, while none of the shoulders with <13.5% glenoid bone loss (n = 47) sustained a recurrent instability event during football (X2 = 15.80, P < .001). Shoulders with >13.5% glenoid bone loss had an incidence rate of 5.31 cases of recurrent instability per 1000 athlete-exposures of football. In 72,000 athlete-exposures to football with <13.5% glenoid bone loss, there was no recurrent instability. Significantly more anchors were used during the primary arthroscopic stabilization procedure in patients who experienced multiple preoperative instability events (P = .005), and lesions spanned significantly more extensive portions along the circumference of the glenoid (P = .001) compared with shoulders having a single preoperative instability event before surgical stabilization.
Conclusion:
Arthroscopic stabilization of anterior shoulder instability in American football players with <13.5% glenoid bone loss provides reliable outcomes and low recurrence rates.
Context. It is generally believed that the supermassive black holes in active galactic nuclei (AGN) and stellar-mass black holes in X-ray binaries (XRBs) work in a similar way. Aims. While XRBs ...evolve rapidly and several sources have undergone a few complete cycles from quiescence to an outburst and back, most AGN remain in the same state over periods of years and decades, due to their longer characteristic timescale proportional to their size. However, the study of the AGN spectral states is still possible with a large sample of sources. Multi-wavelength observations are needed for this purpose since the AGN thermal disc emission dominates in the ultraviolet energy range, while the up-scattered hot-corona emission is detected in X-rays. Methods. We compared simultaneous UV and X-ray measurements of AGN obtained by the XMM-Newton satellite. The non-thermal power-law flux was constrained from the 2−12 keV X-ray luminosity, while the thermal disc component was estimated from the UV flux at ≈ 2900 Å. The hardness (defined as a ratio between the X-ray and UV plus X-ray luminosity) and the total luminosity were used to construct the AGN state diagrams. For sources with reliable mass measurements, the Eddington ratio was used instead of the total luminosity. Results. The state diagrams show that the radio-loud sources have on average higher hardness, due to the lack of the thermal disc emission in the UV band, and have flatter intrinsic X-ray spectra. In contrast, the sources with high luminosity and low hardness are radio-quiet AGN with the UV spectrum consistent with the multi-temperature thermal disc emission. The hardness-Eddington ratio diagram reveals that the average radio-loudness is stronger for low-accreting sources, while it decreases when the accretion rate is close to the Eddington limit. Conclusions. Our results indicate that the general properties of AGN accretion states are similar to those of XRBs. This suggests that the AGN radio dichotomy of radio-loud and radio-quiet sources can be explained by the evolution of the accretion states.
Context.
The stellar mass (
M
⋆
) and the star formation rate (SFR) are among the most important features that characterize galaxies. Measuring these fundamental properties accurately is critical for ...understanding the present state of galaxies, their history, and future evolution. Infrared (IR) photometry is widely used to measure the
M
⋆
and SFR of galaxies because the near-IR traces the continuum emission of the majority of their stellar populations (SPs), and the mid/far-IR traces the dust emission powered by star-forming activity.
Aims.
This work explores the dependence of the IR emission of galaxies on their extinction, and the age of their SPs. It aims to provide accurate and precise IR-photometry SFR and
M
⋆
calibrations that account for SP age and extinction while providing quantification of their scatter.
Methods.
We used the
CIGALE
spectral energy distribution (SED) fitting code to create model SEDs of galaxies with a wide range of star formation histories, dust content, and interstellar medium properties. We fit the relations between
M
⋆
and SFR with IR and optical photometry of the model-galaxy SEDs with the Markov chain Monte Carlo (MCMC) method. As an independent confirmation of the MCMC fitting method, we performed a machine-learning random forest (RF) analysis on the same data set. The RF model yields similar results to the MCMC fits, thus validating the latter.
Results.
This work provides calibrations for the SFR using a combination of the WISE bands 1 and 3, or the JWST NIR-
F
200
W
and MIRI-
F
2100
W
. It also provides mass-to-light ratio calibrations based on the WISE band-1, the JWST NIR-
F
200
W
, and the optical
u
−
r
or
g
−
r
colors. These calibrations account for the biases attributed to the SP age, while they are given in the form of extinction-dependent and extinction-independent relations.
Conclusions.
The proposed calibrations show robust estimations while minimizing the scatter and biases throughout a wide range of SFRs and stellar masses. The SFR calibration offers better results, especially in dust-free or passive galaxies where the contributions of old SPs or biases from the lack of dust are significant. Similarly, the
M
⋆
calibration yields significantly better results for dusty and high-SFR galaxies where dust emission can otherwise bias the estimations.
In 2001, as part of my non-profit work I led a team that went to the United Nations in Geneva and for the first time, put the issue of male circumcision as a human rights violation in the United ...Nations record. For a decade, I felt that no other single event in my life has so strongly affected me as this mutilation of my body that occurred in the first days of my life. ...in 1994, I did do a particularly powerful form of breathwork in a workshop during which I accessed body memories of the event. Based on my experiences with my non-profit, while awareness is growing that children should be left intact so they can make their own decision upon reaching adulthood, changes are coming more slowly than I expected.
► The kinetics of generation and annihilation of vacancies is modeled. ► Dislocation jogs, grain boundaries and Frank loops act as sources and sinks. ► The kinetics is determined by the densities of ...considered objects. ► The vacancy concentration kinetics reflects the thermo-mechanical treatment.
The equilibrium site fraction of vacancies increases with temperature and, thus, annealing and rapid quenching may lead to states with a significant vacancy supersaturation. Excess vacancies can then gradually annihilate at available sinks represented by jogs at dislocations, by grain boundaries or free surfaces. Significant supersaturation by vacancies may also lead to the nucleation and growth of Frank loops acting as additional sinks. Three models corresponding to three different annihilation mechanisms are developed in this paper. They refer to annihilation of excess vacancies at jogs at dislocation with a constant density, at homogeneously distributed Frank loops with a constant density and at grain boundaries. The simulations based on the models are performed for individual annihilation mechanisms under isothermal and non-isothermal conditions as well as for simultaneous annihilation of vacancies at Frank loops and dislocation jogs and grain boundaries using different cooling conditions.
ABSTRACT
We present the results from an X-ray variability study of IRAS 13224-3809. This is probably the best source for X-ray reverberation studies since it is X-ray bright, extremely variable, and ...it has been extensively observed with XMM–Newton. We used all the archival XMM–Newton data from the three EPIC cameras (to increase the signal to noise) and, given the many observations of the source, we were able to compute the time lags spectra in three different flux levels/periods. We fitted the time lags and energy spectra, simultaneously, using a new X-ray reverberation code that computes the time-dependent reflection spectra of the disc as a response to an X-ray flash from a point source located on the axis of the black hole (BH) accretion disc (lamp-post geometry). To the best of our knowledge, this is the first time for active galactic nuclei that both time lags and energy spectra are fitted by a model simultaneously in different flux periods. The model fits in the case when the BH is rapidly rotating are significantly better than the model fits in the case of a Schwarzschild BH. This result strongly favours the hypothesis of a rotating central BH in this source. We also detect significant variations in the height of the X-ray corona. The X-ray height appears to increase from ∼3–5 gravitational radii when the X-ray luminosity is of the order of ∼1.5–3 per cent of the Eddington limit, up to ∼10 gravitational radii, when the luminosity doubles.
Green Peas in X-Rays Svoboda, J.; Douna, V.; Orlitová, I. ...
The Astrophysical journal,
08/2019, Letnik:
880, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
Green Peas represent a population of compact, highly star-forming dwarf galaxies at redshifts
z
∼ 0.2–0.3 that have recently been found to show signatures of ultraviolet ionizing radiation ...leakage. They are being considered as analogs to high-redshift star-forming galaxies, possibly responsible for cosmic reionization. Despite intensive studies of Green Peas in the ultraviolet and optical domains, their X-ray properties have only so far been probed by nearby analogs. In this paper, we present the first measurements of Green Peas in the X-ray domain to constrain their spectral properties and fluxes at high energies. We analyzed
XMM-Newton
observations of three Green Pea sources. For two of them, we found an X-ray luminosity exceeding by a half-order of magnitude its predicted value, derived from the star formation rate and metallicity. Only an upper limit of the X-ray luminosity was derived for the third studied galaxy. Our results indicate that at least some Green Peas produce copious amounts of highly energetic photons, larger than detected in other star-forming galaxies. We discuss possible physical scenarios for the measured X-ray excess, including the presence of a hidden active galactic nucleus, a larger population of X-ray binaries, or ultra-luminous X-ray sources. Future spatially resolved X-ray images will discriminate between the models. Larger Green Pea samples will provide a possible link between the X-ray properties and the leaking ultraviolet radiation.
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