Simple Collapse Research Articles

CHEX-MATE: The intracluster medium entropy distribution in the gravity-dominated regime

We characterise the intracluster gas entropy profiles of 32 very high-mass ($M_ $ M$_ odot Planck SZ-detected galaxy clusters (HIGHMz), selected from the CHEX-MATE sample, allowing us to study the intracluster medium (ICM) entropy distribution in a regime where non-gravitational effects are expected to be minimised. Using XMM- Newton measurements, we determined the entropy profiles up to $ $ for all objects. We assessed the relative role of gas density and temperature measurements on the uncertainty in entropy reconstruction, showing that in the outer regions the largest contribution comes from the temperature. The scaled profiles exhibit a large dispersion in the central regions, but converge rapidly to the value expected from simple gravitational collapse beyond the core regions. We quantified the correlation between the ICM morphological parameters and scaled entropy as a function of radius, showing that centrally peaked objects have low central entropy, while morphologically disturbed objects have high central entropy. We compared the scaled HIGHMz entropy profiles to results from other observational samples, finding differences in normalisation, which appear linked to the average mass of the samples in question. Combining HIGHMz with other samples, we found that a weaker mass dependence than self-similar in the scaling ($A_m -0.25$) allows us to minimise the dispersion in the radial range $ for clusters spanning over a decade in mass. The deviation from self-similar predictions is radially dependent and is more pronounced at small and intermediate radii than at $R_ $. We also investigated the distribution of central entropy $K_0$, finding no evidence for bimodality in the data and outer slope alpha , which peaks at $ 1.1$ with tails at both low and high alpha that correlate with dynamical state. Using weak-lensing masses for half of the sample, we found an indication for a small suppression of the scatter ($ beyond the core when using masses derived from $Y_X$ in the rescaling. Finally, we compared our results to recent cosmological numerical simulations from HE T HREE H UNDRED and MACSIS, finding good agreement with the observational data in this mass regime. These results provide a robust observational benchmark in the gravity-dominated regime, and will serve as a future reference for samples at lower masses, higher redshifts, and for ongoing work using cosmological numerical simulations.

Mitochondrial DNA in bronchoalveolar lavage fluid is associated with the prognosis of idiopathic pulmonary fibrosis: a single cohort study

BackgroundExtracellular mitochondrial DNA (mtDNA) is released from damaged cells and increases in the serum and bronchoalveolar lavage fluid (BALF) of idiopathic pulmonary fibrosis (IPF) patients. While increased levels of serum mtDNA have been reported to be linked to disease progression and the future development of acute exacerbation (AE) of IPF (AE-IPF), the clinical significance of mtDNA in BALF (BALF-mtDNA) remains unclear. We investigated the relationships between BALF-mtDNA levels and other clinical variables and prognosis in IPF.MethodsExtracellular mtDNA levels in BALF samples collected from IPF patients were determined using droplet-digital PCR. Levels of extracellular nucleolar DNA in BALF (BALF-nucDNA) were also determined as a marker for simple cell collapse. Patient characteristics and survival information were retrospectively reviewed.ResultsmtDNA levels in serum and BALF did not correlate with each other. In 27 patients with paired BALF samples obtained in a stable state and at the time of AE diagnosis, BALF-mtDNA levels were significantly increased at the time of AE. Elevated BALF-mtDNA levels were associated with inflammation or disordered pulmonary function in a stable state (n = 90), while being associated with age and BALF-neutrophils at the time of AE (n = 38). BALF-mtDNA ≥ 4234.3 copies/µL in a stable state (median survival time (MST): 42.4 vs. 79.6 months, p < 0.001) and ≥ 11,194.3 copies/µL at the time of AE (MST: 2.6 vs. 20.0 months, p = 0.03) were associated with shorter survival after BALF collection, even after adjusting for other known prognostic factors. On the other hand, BALF-nucDNA showed different trends in correlation with other clinical variables and did not show any significant association with survival time.ConclusionsElevated BALF-mtDNA was associated with a poor prognosis in both IPF and AE-IPF. Of note, at the time of AE, it sharply distinguished survivors from non-survivors. Given the trends shown by analyses for BALF-nucDNA, the elevation of BALF-mtDNA might not simply reflect the impact of cell collapse. Further studies are required to explore the underlying mechanisms and clinical applications of BALF-mtDNA in IPF.

Unchannelized granular flows: Effect of initial granular column geometry on fluid dynamics

In recent years, significant progress has been made in modelling granular flows using the μI-rheology model, which connects the viscosity of a granular medium to the pressure and strain rate via a dimensionless quantity called the inertial number, I. This model allows treating the granular material as a non-Newtonian liquid with a yield stress, making it possible to model the flow using the continuum approach, which is less computationally expensive than discrete element methods.In this paper, we implement the μI-rheology model in a computational fluid dynamics (CFD) code and couple it with the volume of fluid (VOF) interface tracking approach to model the three-dimensional (3D) flow of monodisperse granular materials. After validating the model using experimental data, we briefly describe a trial-and-error method for evaluating the material properties of powders via a simple collapse experiment. Then, employing the CFD model, we investigate the physics of the unchannelized collapse of granular materials and perform an energy budget analysis to demonstrate the different stages of the granular collapse.To further investigate the effect of the initial shape of the pile on the spreading dynamics, we run a campaign of 3D simulations. Our results show that the μI-rheology model accurately reproduces the dynamics of the granular material during the collapse and can be used for risk assessment purposes in natural disasters. The findings from our simulations can also aid in developing preventative measures to minimize potential harm.

Elastic Shakedown and Roughness Evolution in Repeated Elastic–Plastic Contact

Surface roughness emerges naturally during mechanical removal of material, fracture, chemical deposition, plastic deformation, indentation, and other processes. Here, we use continuum simulations to show how roughness which is neither Gaussian nor self-affine emerges from repeated elastic–plastic contact of rough and rigid surfaces on a flat elastic–plastic substrate. Roughness profiles change with each contact cycle, but appear to approach a steady-state long before the substrate stops deforming plastically and has hence “shaken-down” elastically. We propose a simple dynamic collapse for the emerging power-spectral density, which shows that the multi-scale nature of the roughness is encoded in the first few indentations. In contrast to macroscopic roughness parameters, roughness at small scales and the skewness of the height distribution of the resulting roughness do not show a steady-state. However, the skewness vanishes asymptotically with contact cycle.Graphical

The degradation mechanisms of a nanobainitic steel under cavitation erosion conditions

The nanobainitic steel was investigated using a chamber with the cavitating jet at two distances from a nozzle. Fe-0.6C-1.7Mn-1.6Si-1.35Cr-0.4Mo steel subjected to austenitising at 950 °C followed by controlled air cooling and the isothermal heat treatment at 215 °C shows high strength and good plasticity. The microstructure of steel consists of packets of laths of carbide-free bainite and 10 % in volume of retained austenite in the form of laths, plates, and grains (blocky). Due to its very good combination of strength and plasticity, nanobainitic steel is promising for applications under extreme loading conditions. For this reason, it was decided to analyse the behaviour of the steel under dynamic loads with high-pressure amplitude. Such conditions are obtained during cavitation erosion tests. The distance from the nozzle affected the degradation process (type of damage, maximum and final erosion rates). Three types of damage were observed: A) caused by simple collapse of the cavitation bubble, B) caused by splitting of the cavitation bubble into two smaller bubbles, and C) caused by fragmentation of the cavitation bubble into many tiny bubbles. Some similarities in the appearance of the damage were observed: dark rings with a changed structure and a recess in the middle, a dark surface layer, a quasi-etched structure with numerous small recesses, and a structure with fine needles. The “needle” structure was formed only after reaching the maximum rate of erosion. As the distance from the nozzle increased, more and more cavitation bubbles fragmented, which resulted in an increase in erosion intensity and the maximum rate of erosion. Higher erosion intensity affected the higher transformation of austenite to martensite and finally rounding/convexity of the entire surface and a decrease in erosion rate.

What moves the heavens above?

The standard cosmological model (ΛCDM) assumes that everything started in a singular Big Bang out of Cosmic Inflation, a mysterious form of modern Aether (the inflaton). Here we look for direct observational evidence for such beginning in two recent measurements: 1) cosmic acceleration, something ΛCDM attributes to Dark Energy (DE), 2) discordant measurements for H0 and anomalies in the CMB. We find here that observed variations in H0 correspond to large metric perturbations that are not consistent with the simplest models of Inflation or DE in the ΛCDM paradigm. Together, these observations indicate instead that cosmic expansion could originate from a simple gravitational collapse and bounce. We conjecture that such bounce is trigger by neutron degeneracy at GeV energies. This new paradigm explains the heavens above using only the known laws of Physics, without any new Aether, DE or Inflation.

Physics of star-formation history and the luminosity function of galaxies therefrom

ABSTRACT We show that the star-formation history, the reionization history and the present luminosity function of galaxies are reproduced in a simple gravitational collapse model within the ΛCDM regime to an almost quantitative accuracy when the physical conditions, the Jeans criterion and the cooling process are taken into account. Taking a reasonable set of model parameters, the reionization takes place sharply at about redshift 1 + z ≃ 7.5, and the resulting luminosity function turns off at $L\simeq 10^{10.7}\, {\rm L}_\odot$, showing the consistency between the star-formation history and the reionization of the Universe. The model gives the total amount of stars Ωstar = 0.004 in units of the critical density, compared with the observational value of 0.0044 with a recycling factor of 1.6. In order to account for the observed star-formation rate and the present luminosity function, the star-formation efficiency is not halo-mass-independent but has a maximum at the halo mass $\simeq 10^{12}\, {\rm M}_\odot$ and is suppressed for both lower- and higher-mass haloes.

Constraining primordial black holes as dark matter using the global 21-cm signal with X-ray heating and excess radio background

Using the global 21-cm signal measurement by the EDGES collaboration, we derive constraints on the fraction of the dark matter that is in the form of primordial black holes (PBHs) with masses in the range 1015–1017 g. Improving upon previous analyses, we consider the effect of the X-ray heating of the intergalactic medium on these constraints, and also use the full shape of the 21-cm absorption feature in our inference. In order to account for the anomalously deep absorption amplitude, we also consider an excess radio background motivated by LWA1 and ARCADE2 observations. Because the heating rate induced by PBH evaporation evolves slowly, the data favour a scenario in which PBH-induced heating is accompanied by X-ray heating. Also, for the same reason, using the full measurement across the EDGES observation band yields much stronger constraints on PBHs than just the redshift of absorption. We find that 21-cm observations exclude f PBH ≳ 10-9.7 at 95% CL for M PBH = 1015 g. This limit weakens approximately as M 4 PBH towards higher masses, thus providing the strongest constraints on ultralight evaporating PBHs as dark matter over the entire mass range 1015–1017 g. Under the assumption of a simple spherical gravitational collapse based on the Press-Schechter formalism, we also derive bounds on the curvature power spectrum at extremely small scales (k ∼ 1015 Mpc-1). This highlights the usefulness of global 21-cm measurements, including non-detections, across wide frequency bands for probing exotic physical processes.

A failure criterion for RC beams subjected to axial and transverse loadings

The upper bound kinematic approach of yield design is developed for the design of reinforced concrete (RC) beams subjected to the combination of transverse and axial loadings. The method is implemented by considering a simple virtual collapse mechanism in which the beam is divided into two rigid blocks separated by a plane. Each block is given a virtual motion of translation as well as of rotation about its support. An optimization of the problem is then formulated, resulting in an upper bound to the strength condition of the RC beam in terms of axial and transverse loading parameters. These theoretical predictions are then compared to the results derived from numerical simulations of the same problem using a finite element-based limit analysis software (which can consider much more complex failure mechanisms than the one considered). Finally, in order to assess their practical validity, predictions from the proposed method are also compared to other predictive methods, as well as to some available experimental results published in the literature.

The fruitful death of modal collapse arguments

Modal collapse arguments are all the rage in certain philosophical circles as of late. The arguments purport to show that classical theism entails the absurdly fatalistic conclusion that everything exists necessarily. My first aim in this paper is bold: to put an end to action-based modal collapse arguments against classical theism. To accomplish this, I first articulate the ‘Simple Modal Collapse Argument’ and then characterize and defend Tomaszewski’s criticism thereof. Second, I critically examine Mullins’ new modal collapse argument formulated in response to the aforementioned criticism. I argue that Mullins’ new argument does not succeed. Third, I critically examine a powers-based modal collapse argument against classical theism that has received much less attention in the literature. Fourth, I show why God’s being purely actual, as well God’s being identical to each of God’s acts, simply cannot entail modal collapse given indeterministic causation. This, I take it, signals the death of modal collapse arguments. But not all hope is lost for proponents of modal collapse arguments—for the death is a fruitful one insofar as it paves the way for new inquiry into at least two new potential problems for classical theism. Showing this is my paper’s second aim.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

Porosity in minerals

&lt;abstract&gt; &lt;p&gt;Minerals typically form porous assemblies with porosity extending from a few percent to ca. 35% in porous sandstones, and over 50% in tuff, clays, and tuff. While transport of gases and liquids are widely researched in these materials, much less is known about their mechanical behaviour under stress. With the development of artificial porous materials such questions become more pertinent, e.g., for applications as fillers in car bumpers and airplane wings, and nanoscale applications in memistors and neuromorphic computers. This article argues that elasticity and related dielectric and magnetic properties can be described‑to some extend-as universal in porous materials. The collapse of porous materials under stress triggers in many cases avalanches of collapsed regions which are scale invariant and follow irreversible power law energy emission. Emphasis is given to a recent simple collapse model by Casals and Salje which covers many of the observed phenomena.&lt;/p&gt; &lt;/abstract&gt;

On the Influence of Angular Momentum and Dynamical Friction on Structure Formation

In this paper we extended the spherical collapse model to take account of angular momentum and dynamical friction and studied how the accreted mass, the threshold of collapse, the virial overdensity, and the mass function change. Solving the equation of motion we got the relationships between mass, M, and the turn-around radius, $${{R}_{0}}$$ . This relation is important because knowing $${{R}_{0}}$$ one can obtain the mass accreted by the structure. We see that moving from the simple spherical collapse to that accounting for angular momentum and dynamical friction leads to the increase of acquired mass. Then, we showed how angular momentum, and dynamical friction change the threshold of collapse with mass, and also with redshift for different dark energy models. We repeated the calculation for the virial overdensity, and the mass function, founding noteworthy differences with the case of the simple spherical collapse.

Advances in Surgical Management of Schatzker III Tibial Plateau Fractures

The tibial plateau Schatzker type Ⅲ fracture is a simple lateral collapse fracture, which is mainly seen in the low energy injuries of the knee joint in older patients with osteoporosis. The treatment options for this type of fracture are open reduction and internal fixation. Repairing the alignment of the collapsed joint surface and the tibial force line is the final goal of surgical treatment. Usually the choice of internal fixation is the combination of ship valve screw arrangement and support steel plate. Many authors recommend avoiding the use of simple hollow screws, especially in comminuted fractures with more severe joint defects, as this can easily lead to secondary collapse of the joint.(5)The traditional surgical method is an anterior-lateral approach with open reduction and internal fixation. Due to the long incision, large trauma, and poor medical compliance of the elderly, it is prone to complicated knee stiffness and traumatic arthritis. The surgical effect is not satisfactory.

Relativistic bias in neutrino cosmologies

Halos and galaxies are tracers of the underlying dark matter structures. While their bias is well understood in the case of a simple Universe composed dominantly of dark matter, the relation becomes more complex in the presence of massive neutrinos. Indeed massive neutrinos introduce rich dynamics in the process of structure formation leading to scale-dependent bias. We study this process from the perspective of general relativity employing a simple spherical collapse model. We find a characteristic signature at the neutrino free-streaming scale in addition to a large-scale feature from general relativity. The scale-dependent halo bias opposes the suppression in the matter distribution due to neutrino free-streaming and leads to corrections of a few percent in the halo power spectrum. It is not only sensitive to the sum of the neutrino-masses, but respond to the individual masses. Accurate models for the neutrino bias are a crucial ingredient for the future data analysis and play an important role in constraining the neutrino masses.

Seismic uplift resistance of circular plate anchors in sand

In the present study, theoretical solutions have been developed for computing the vertical seismic uplift resistance of a shallow buried horizontal circular plate anchor in sand with the incorporation of shear transfer at the interface of the anchor plate and overlying sand during an earthquake. The analysis was performed by employing the kinematic theorem of limit analysis based on a pseudo-static approach, with the assumption of a simple rigid wedge collapse mechanism in the form of an inverted frustum with cross-section changing from circular at the anchor level to an elliptical shape at any level just above the anchor. The effect of seismic body forces on the uplift capacity of the circular anchor is evaluated in terms of dimensionless seismic factors Sq and Sγ due to the components of surcharge pressure and soil unit weight, respectively. An increase in the magnitude of seismic acceleration leads to a continuous reduction in uplift resistance; a significant decrease in the uplift resistance was found to occur for the case with the consideration of shear at the interface between the anchor top surface and the soil as compared to that without any shear.

Universal thermodynamic properties of the intracluster medium over two decades in radius in the X-COP sample

Context.The hot plasma in a galaxy cluster is expected to be heated to high temperatures through shocks and adiabatic compression. The thermodynamical properties of the gas encode information on the processes leading to the thermalization of the gas in the cluster’s potential well and on non-gravitational processes such as gas cooling, AGN feedback, shocks, turbulence, bulk motions, cosmic rays and magnetic field.Aims.In this work we present the radial profiles of the thermodynamic properties of the intracluster medium (ICM) out to the virial radius for a sample of 12 galaxy clusters selected from thePlanckall-sky survey. We determine the universal profiles of gas density, temperature, pressure, and entropy over more than two decades in radius, from 0.01R500to 2R500.Methods.We exploited X-ray information fromXMM-Newtonand Sunyaev-Zel’dovich constraints fromPlanckto recover thermodynamic properties out to 2R500. We provide average functional forms for the radial dependence of the main quantities and quantify the slope and intrinsic scatter of the population as a function of radius.Results.We find that gas density and pressure profiles steepen steadily with radius, in excellent agreement with previous observational results. Entropy profiles beyondR500closely follow the predictions for the gravitational collapse of structures. The scatter in all thermodynamical quantities reaches a minimum in the range [0.2 − 0.8]R500and increases outward. Somewhat surprisingly, we find that pressure is substantially more scattered than temperature and density.Conclusions.Our results indicate that once accreting substructures are properly excised, the properties of the ICM beyond the cooling region (R &gt; 0.3R500) follow remarkably well the predictions of simple gravitational collapse and require few non-gravitational corrections.

Quantum Zeno Effect assisted Spectroscopy of a single trapped Ion

The quantum Zeno effect (QZE) is not only interesting as a manifestation of the counterintuitive behavior of quantum mechanics, but may also have practical applications. When a spectroscopy laser is applied to target atoms or ions prepared in an initial state, the Rabi flopping of an auxiliary transition sharing one common level can be inhibited. This effect is found to be strongly dependent on the detuning of the spectroscopy laser and offers a sensitive spectroscopy signal which allows for high precision spectroscopy of transitions with a small excitation rate. We demonstrate this method with direct frequency comb spectroscopy using the minute power of a single mode to drive a dipole allowed transition in a single trapped ion. Resolving the individual modes of the frequency comb demonstrates that the simple instantaneous quantum collapse description of the QZE can not be applied here, as these modes need several pulses to build up.

Vertical uplift capacity of a group of shallow circular plate anchors in sand

ABSTRACTThe uplift capacity of a group of circular plate anchors buried horizontally in sand along a line has been determined. The uplift capacity of an interfering anchor is presented in terms of nondimensional uplift factors, Fγi and Fqi, due to components of soil unit weight and surcharge pressure acting on the ground surface, respectively. Theoretical solutions have been developed by applying the upper bound theorem of limit analysis based on a simple rigid wedge collapse mechanism. In the case of two and infinite number of anchors, closed-form solutions have been developed for computing the factor Fqi, whereas the factor Fγi is determined using a semianalytical approach. As expected, the interference of the anchors leads to a continuous reduction in the uplift resistance with a decrease in the spacing between the anchors, and the uplift resistance decreases with the increasing number of anchors at a given spacing. The results compare reasonably well with the available theoretical and experimental data from the literature.

British Fictions after Devolution: William Boyd’s Culinary Arts

Taking William Boyd's post-2000 novels as symptomatic of wider problems in British writing during the period of the break-up of Britain, this essay suggests that what looks, at first, like a simple collapse in Boyd's talent in fact has produced texts illuminating, in their limitations, the difficulties of British affiliation in the era of Britishness's ideological exhaustion. Boyd is, on this reading, an exemplary counter-example to the canon of self-consciously Scottish fiction more commonly studied in the years since 1979.