Letteratura scientifica selezionata sul tema "Fraction massique"

Les populations ouest africaines produisent de grandes quantites de recoltes. Malheureusement faute de moyens de conservation, ces produits pourrissent. Cest pour cette raison que nous nous sommes interesses au sechage solaire des produits agro-alimentaires avec comme produit la banana douce. Lobjectif de cette publication est letude des performances thermiques dun sechoir solaire à absorbeur à ailettes. Les materiels utilises sont : un sechoir complet constitue de cinq claies, des tranches de banane douce, dune balance de precision et dun enregistreur automatique de temperatures. Levolution de la teneur en eau nous a montre que 65% de leau des rondelles est eliminee le 1er jour et 20% le 2eme jour. Les courbes simulees de sechage traduisent que la fraction massique de la vapeur deau dans lair augmente et celle du fruit diminue car lair shumidifie par absorption deau du produit. Enfin les performances thermiques du sechoir solaire sont estimees par la masse de banane sechee et lintroduction des ailettes a developpe un ecoulement turbulent.

ABSTRACT Galaxy mergers are instrumental in dictating the final mass, structure, stellar populations, and kinematics of galaxies. Cosmological galaxy simulations indicate that the most massive galaxies at z = 0 are dominated by high fractions of ‘ex-situ’ stars, which formed first in distinct independent galaxies, and then subsequently merged into the host galaxy. Using spatially resolved MUSE spectroscopy we quantify and map the ex-situ stars in thirteen massive early-type galaxies. We use full spectral fitting together with semi-analytic galaxy evolution models to isolate the signatures in the galaxies’ light which are indicative of ex-situ populations. Using the large MUSE field of view we find that all galaxies display an increase in ex-situ fraction with radius, with massive and more extended galaxies showing a more rapid increase in radial ex-situ fraction (reaching values between ∼30 per cent and 100 per cent at 2 effective radii) compared to less massive and more compact sources (reaching between ∼5 per cent and 40 per cent ex-situ fraction within the same radius). These results are in line with predictions from theory and simulations which suggest ex-situ fractions should increase significantly with radius at fixed mass for the most massive galaxies.

Abstract We explore the characteristics of actively accreting massive black holes (MBHs) within dwarf galaxies in the Romulus25 cosmological hydrodynamic simulation. We examine the MBH occupation fraction, X-ray active fractions, and active galactic nucleus (AGN) scaling relations within dwarf galaxies of stellar mass 108 M ⊙ < M star < 1010 M ⊙ out to redshift z = 2. In the local universe, the MBH occupation fraction is consistent with observed constraints, dropping below unity at M star < 3 × 1010 M ⊙, M 200 < 3 × 1011 M ⊙. Local dwarf AGN in Romulus25 follow observed scaling relations between AGN X-ray luminosity, stellar mass, and star formation rate, though they exhibit slightly higher active fractions and number densities than comparable X-ray observations. Since z = 2, the MBH occupation fraction has decreased, the population of dwarf AGN has become overall less luminous, and as a result the overall number density of dwarf AGN has diminished. We predict the existence of a large population of MBHs in the local universe with low X-ray luminosities and high contamination from X-ray binaries and the hot interstellar medium that are undetectable by current X-ray surveys. These hidden MBHs make up 76% of all MBHs in local dwarf galaxies and include many MBHs that are undermassive relative to their host galaxy’s stellar mass. Their detection relies on not only greater instrument sensitivity but also better modeling of X-ray contaminants or multiwavelength surveys. Our results indicate that dwarf AGN were substantially more active in the past, despite having low luminosity today, and that future deep X-ray surveys may uncover many hidden MBHs in dwarf galaxies out to at least z = 2.

AbstractWe probe how common extremely rapid rotation is among massive stars in the early universe by measuring the OBe star fraction in nearby metal-poor dwarf galaxies. We apply a new method that uses broad-band photometry to measure the galaxy-wide OBe star fractions in the Magellanic Clouds and three more distant, more metal-poor dwarf galaxies. We find OBe star fractions of ∼20% in the Large Magallanic Cloud (0.5Zȯ), and ∼30% in the Small Magellanic Cloud (0.2Zȯ) as well as in the so-far unexplored metallicity range 0.1 Z/Zȯ < 0.2 occupied by the other three dwarf galaxies. Our results imply that extremely rapid rotation is common among massive stars in metal-poor environments such as the early universe.

Abstract We investigate the role of halo concentration in the formation of intracluster light (ICL) in galaxy groups and clusters, as predicted by a state-of-the-art semianalytic model of galaxy formation, coupled with a set of high-resolution dark-matter-only simulations. The analysis focuses on how the fraction of ICL correlates with halo mass, concentration, and fraction of early-type galaxies (ETGs) in a large sample of groups and clusters with 13.0 ≤ log M halo ≤ 15.0 . The fraction of ICL follows a normal distribution, a consequence of the stochastic nature of the physical processes responsible for the formation of the diffuse light. The fractional budget of ICL depends on both halo mass (very weakly) until group scales, and concentration (remarkably). More interestingly, the ICL fraction is higher in more concentrated objects, a result of the stronger tidal forces acting in the innermost regions of the halos where the concentration is the quantity playing the most relevant role. Our model predictions do not show any dependence between the ICL and ETGs fractions, and so we instead suggest the concentration rather than the mass, as recently claimed, to be the main driver of the ICL formation. The diffuse light starts to form in groups via stellar stripping and mergers and later assembled in more-massive objects. However, the formation and assembly keep going on group/cluster scales at lower redshift through the same processes, mainly via stellar stripping in the vicinity of the central regions where tidal forces are stronger.

AbstractMost massive stars (up to 100%) are thought to be in binary systems. The multiplicity of massive stars seems to be intrinsically linked to their formation and evolution, and so Massive Young Stellar Objects are key in observing this early stage of star formation. We have surveyed hundreds of MYSOs across the Galaxy from the RMS catalogue, using UKIDSS and VVV point source data. Preliminary results show binary fractions of 44±3% for the UKIDSS sample and 32±3% for the VVV sample. In addition we use the K-band magnitudes as a proxy for the companion mass, and find a significant fraction of the detected companions have estimated mass ratios greater than 0.5, which suggests a deviation from the capture formation scenario.

ABSTRACT The central dark-matter fraction of galaxies is sensitive to feedback processes during galaxy formation. Strong gravitational lensing has been effective in the precise measurement of the dark-matter fraction inside massive early-type galaxies. Here, we compare the projected dark-matter fraction of early-type galaxies inferred from the SLACS (Sloan Lens ACS Survey) strong-lens survey with those obtained from the Evolution and Assembly of GaLaxies and their Environment (EAGLE), Illustris, and IllustrisTNG hydrodynamical simulations. Previous comparisons with some simulations revealed a large discrepancy, with considerably higher inferred dark-matter fractions – by factors of ≈2–3 – inside half of the effective radius in observed strong-lens galaxies as compared to simulated galaxies. Here, we report good agreement between EAGLE and SLACS for the dark-matter fractions inside both half of the effective radius and the effective radius as a function of the galaxy’s stellar mass, effective radius, and total mass-density slope. However, for IllustrisTNG and Illustris, the dark-matter fractions are lower than observed. This work consistently assumes a Chabrier initial mass function (IMF), which suggests that a different IMF (although not excluded) is not necessary to resolve this mismatch. The differences in the stellar feedback model between EAGLE and Illustris and IllustrisTNG are likely the dominant cause of the difference in their dark-matter fraction and density slope.

ABSTRACT Theoretical models suggest that galaxy mergers may have profoundly shaped galaxy morphologies through cosmic time. However, observational estimates of galaxy pair fractions, and implied galaxy mergers, still do not converge, suggesting different numbers and redshift evolution. This paper explores the connection between stellar mass estimation and the pair fraction of galaxies using $\rm {\small STEEL}$, the Statistical sEmi-Emprical modeL, in which galaxies are mapped on to host dark matter haloes via a stellar mass–halo mass (SMHM) relation. As haloes of different mass are predicted to undergo, on average, different degrees of mergers, we expect that galaxy merger rates at fixed stellar mass will also vary depending on the shape of the input SMHM relation. Using a variety of input SMHM relations, also including one that matches the outputs of the Illustris TNG simulation, we thoroughly explore how systematic variations in the stellar mass functions propagate on to the normalization and redshift dependence of the galaxy pair fraction. We find that (i) stellar mass functions characterized by larger number densities of massive galaxies and thus a steeper SMHM relation, result in a substantial reduction of the pair fractions of massive galaxies; (ii) a time-varying SMHM relation produces galaxy pair fractions that can have varied redshift evolutions. We argue that in a hierarchical, dark matter dominated Universe, stellar mass estimates are a considerable cause of bias that must be accounted for when comparing pair fractions from different data sets or from theoretical models developed independently of the fitted survey data.

ABSTRACT The physical origin of low escape fractions of ionizing radiation derived from massive star-forming galaxies at z ∼ 3–4 is not well understood. We perform idealized disc galaxy simulations to understand how galactic properties such as metallicity and gas mass affect the escape of Lyman continuum (LyC) photons using radiation-hydrodynamic simulations with strong stellar feedback. We find that the luminosity-weighted escape fraction from a metal-poor (Z = 0.002) galaxy embedded in a halo of mass $M_{\rm h}\simeq 10^{11}\, \mathrm{M}_\odot$ is $\left\langle {f_{\rm esc}^{\rm 3D}}\right\rangle \simeq 10\, {{\ \rm per\ cent}}$. Roughly half of the LyC photons are absorbed within scales of 100 pc, and the other half is absorbed in the ISM ($\lesssim 2\, {\rm kpc}$). When the metallicity of the gas is increased to Z = 0.02, the escape fraction is significantly reduced to $\left\langle {f_{\rm esc}^{\rm 3D}}\right\rangle \simeq 1{{\ \rm per\ cent}}$ because young stars are enshrouded by their birth clouds for a longer time. In contrast, increasing the gas mass by a factor of 5 leads to $\left\langle {f_{\rm esc}^{\rm 3D}}\right\rangle \simeq 5\, {{\ \rm per\ cent}}$ because LyC photons are only moderately absorbed by the thicker disc. Our experiments suggest that high metallicity is likely more responsible for the low escape fractions observed in massive star-forming galaxies, supporting the scenario in which the escape fraction is decreasing with increasing halo mass. Finally, negligible correlation is observed between the escape fraction and surface density of star formation or galactic outflow rates.

Abstract To figure out the effect of stellar mass and local environment on morphological transformation and star formation quenching in galaxies, we use the massive (M * ≥ 1010 M ⊙) galaxies at 0.5 ≤ z ≤ 2.5 in five fields of 3D-HST/CANDELS. Based on the UVJ diagnosis and the possibility of possessing a spheroid, our sample of massive galaxies is classified into four populations: quiescent early-type galaxies (qEs), quiescent late-type galaxies (qLs), star-forming early-type galaxies (sEs), and star-forming late-type galaxies (sLs). It is found that the quiescent fraction is significantly elevated at the high ends of mass and local environmental overdensity, which suggests a clear dependence of quenching on both mass and local environment. Over cosmic time, the mass dependence of galaxy quiescence decreases while the local environment dependence increases. The early-type fraction is found to be larger only at the high-mass end, indicating an evident mass dependence of morphological transformation. This mass dependence becomes more significant at lower redshifts. Among the four populations, the fraction of active galactic nuclei (AGNs) in the qLs peaks at 2 < z ≤ 2.5, and rapidly declines with cosmic time. The sEs are found to have higher AGN fractions of 20%–30% at 0.5 ≤ z < 2 . The redshift evolution of AGN fractions in the qLs and sEs suggests that AGN feedback could have played important roles in the formation of the qLs and sEs.

Les clusters légers dans la matière nucléaire apparaissent à des densités inférieures à la densité de saturation nucléaire. Ils peuvent jouer un rôle important dans des scénarios astrophysiques comme les supernovae à effondrement de cœur, où les propriétés de la matière nucléaire influence la propagation de l'onde de choc et le parcours des neutrinos émis. À de telles densités, des effets de milieu sont présents et modifient les propriétés des clusters formés, leur abondance et, par conséquent, la dynamique des supernovae. Nous avons utilisé un modèle champ moyen relativiste (RMF) avec des clusters comme degrés de liberté explicites et des échanges de mésons virtuels. Ce modèle possède un couplage clusters-méson empirique qui nécessite d’être calibré avec des observations expérimentales. À partir des collisions d'ions lourds, nous avons sélectionné des événements afin de construire différents ensembles statistiques correspondant à des conditions thermodynamiques particulières. Dans ces ensembles, nous avons extrait les compositions chimiques en terme de fractions massique des isotopes d’hydrogène et d’hélium. En parallèle, nous avons renforcé l’utilisation de l’hypothèse d’équilibre par l’étude des propriétés d’isoscaling. Enfin, dans une analyse bayésienne, nous avons comparé les ensembles expérimentaux avec des calculs issus du modèle RMF, où la densité, la température et le couplage clusters-méson sont libres. Nous avons réussi à reproduire les fractions massiques expérimentales des différents clusters, en considérant une densité unique pour chaque ensemble. Pour étudier les limites de cette analyse et l’étendre à d’autres systèmes, une nouvelle expérience a été réalisée avec le multidétecteur INDRA-FAZIA. D’importantes améliorations ont été apportées sur le dispositif, ce qui a permis d’améliorer significativement ses performances, notamment en termes d’identification isotopique. Ainsi, la quasi-totalité du travail de réduction des données (calibration en énergie et identification) a été achevée pour cette nouvelle expérience. Dans le cadre d'une étude préliminaire, l'analyse a été initiée sur les événements de type vaporisation, mais elle nécessite des efforts supplémentaires
Light clusters in nuclear matter appear at densities below nuclear saturation density. They can play an important role in astrophysical scenarios like core-collapse supernovae, where the properties of nuclear matter influence the shock wave propagation and the path of emitted neutrinos. At such densities, in-medium effects are present and modify the properties of the formed clusters, their abundance, and, consequently, the dynamics of supernovae. We used a relativistic mean field (RMF) model with clusters as explicit degrees of freedom and virtual meson exchanges. This model includes an empirical cluster-meson coupling that requires calibration with experimental observations. From heavy ion collisions, we selected events to construct different statistical ensembles corresponding to particular thermodynamic conditions. In these ensembles, we extracted the chemical compositions in terms of the mass fractions of hydrogen and helium isotopes. In parallel, we strengthened the use of the equilibrium hypothesis by studying isoscaling properties. Finally, in a Bayesian analysis, we compared the experimental ensembles with calculations from the RMF model, where density, temperature, and cluster-meson coupling are free parameters. We successfully reproduced the experimental mass fractions of the various clusters, considering a unique density for each ensemble. To explore the limitations of this analysis and extend it to other systems, a new experiment was conducted with the INDRA-FAZIA multidetector. Significant improvements were made to the device, which has considerably enhanced its performance, particularly in terms of isotopic identification. Consequently, nearly all of the data reduction work (energy calibration and identification) has been completed for this new experiment. In a preliminary study, the analysis began on vaporization-type events, but further efforts are required

We study the galaxy populations in 74 Sunyaev-Zeldovich effect selected clusters from the South Pole Telescope survey, which have been imaged in the science verification phase of the Dark Energy Survey. The sample extends up to z similar to 1.1 with 4 x 10(14)M(circle dot) <= M-200 <= 3 x 10(15)M(circle dot). Using the band containing the 4000 angstrom break and its redward neighbour, we study the colour-magnitude distributions of cluster galaxies to similar to m(*) + 2, finding that: (1) The intrinsic rest frame g - r colour width of the red sequence (RS) population is similar to 0.03 out to z similar to 0.85 with a preference for an increase to similar to 0.07 at z = 1, and (2) the prominence of the RS declines beyond z similar to 0.6. The spatial distribution of cluster galaxies is well described by the NFW profile out to 4R(200) with a concentration of c(g) = 3.59(-0.18)(+0.20), 5.37(-0.24)(+0.27) and 1.38(-0.19)(+0.21) for the full, the RS and the blue non-RS populations, respectively, but with similar to 40 per cent to 55 per cent cluster to cluster variation and no statistically significant redshift or mass trends. The number of galaxies within the virial region N-200 exhibits a mass trend indicating that the number of galaxies per unit total mass is lower in the most massive clusters, and shows no significant redshift trend. The RS fraction within R-200 is (68 +/- 3) per cent at z = 0.46, varies from similar to 55 per cent at z = 1 to similar to 80 per cent at z = 0.1 and exhibits intrinsic variation among

Owing to its ability to improve both spectral and energy efficiency of wireless networks, massive multiple-input multiple-output (mMIMO) has become one of the key enablers of the fifth-generation (5G) and beyond communication systems. For successful integration of this promising physical layer technique in the upcoming cellular standards, it is essential to have a comprehensive understanding of its network-level performance. Over the last decade, stochastic geometry has been instrumental in obtaining useful system design insights of wireless networks through accurate and tractable theoretical analysis. Hence, it is only natural to consider modeling and analyzing the mMIMO systems using appropriate statistical constructs from the stochastic geometry literature and gain insights for its future implementation. With this broader objective in mind, we first focus on modeling a cellular mMIMO network that uses fractional pilot reuse to mitigate the sole performance-limiting factor of mMIMO networks, namely, pilot contamination. Leveraging constructs from the stochastic geometry literature, such as Johnson-Mehl cells, we derive analytical expressions for the uplink (UL) signal-to-interference-and-noise ratio (SINR) coverage probability and average spectral efficiency for a random user. From our system analysis, we present a partitioning rule for the number of pilot sequences to be reserved for the cell-center and cell-edge users that improves the average cell-edge user spectral efficiency while achieving similar cell-center user spectral efficiency with respect to unity pilot reuse. In addition, using the analytical approach developed for the cell-center user performance evaluation, we study the performance of a small cell system where user and base station (BS) locations are coupled. The impact of distance-dependent UL power control on the performance of an mMIMO network with unity pilot reuse is analyzed and subsequent system design guidelines are also presented. Next, we focus on the performance analysis of the cell-free mMIMO network, which is a distributed implementation of the mMIMO system that leads to the second and third contributions of this dissertation. Similar to the cellular counterpart, the cell-free systems also suffer from pilot contamination due to the reuse of pilot sequences throughout the network. Inspired by a hardcore point process known as the random sequential adsorption (RSA) process, we develop a new distributed pilot assignment algorithm that mitigates the effect of pilot contamination by ensuring a minimum distance among the co-pilot users. This pilot assignment scheme leads to the construction of a new point process, namely the multilayer RSA process. We study the statistical properties of this point process both in one and two-dimensional spaces by deriving approximate but accurate expressions for the density and pair correlation functions. Leveraging these new results, for a cell-free network with the proposed RSA-based pilot assignment scheme, we present an analytical approach that determines the minimum number of pilots required to schedule a user with probabilistic guarantees. In addition, to benchmark the performance of the RSA-based scheme, we propose two optimization-based centralized pilot allocation schemes using linear programming principles. Through extensive numerical simulations, we validate the efficacy of the distributed and scalable RSA-based pilot assignment scheme compared to the proposed centralized algorithms. Apart from pilot contamination, another impediment to the performance of a cell-free mMIMO is limited fronthaul capacity between the baseband unit and the access points (APs). In our fourth contribution, using appropriate stochastic geometry-based tools, we model and analyze the downlink of such a network for two different implementation scenarios. In the first scenario, we consider a finite network where each AP serves all the users in the network. In the second scenario, we consider an infinite network where each user is served by a few nearby APs in order to limit the load on fronthaul links. From our analyses, we observe that for the finite network, the achievable average system sum-rate is a strictly quasi-concave function of the number of users in the network, which serves as a key guideline for scheduler design for such systems. Further, for the user-centric architecture, we observe that there exists an optimal number of serving APs that maximizes the average user rate. The fifth and final contribution of this dissertation focuses on the potential improvement that is possible by the use of mMIMO in citizen broadband radio service (CBRS) spectrum sharing systems. As a first concrete step, we present comprehensive modeling and analysis of this system with omni-directional transmissions. Our model takes into account the key guidelines by the Federal Communications Commission for co-existence between licensed and unlicensed networks in the 3.5 GHz CBRS frequency band. Leveraging the properties of the Poisson hole process and Matern hardcore point process of type II, a.k.a. ghost RSA process, we analytically characterize the impact of different system parameters on various performance metrics such as medium access probability, coverage probability, and area spectral efficiency. Further, we provide useful system design guidelines for successful co-existence between these networks. Building upon this omni-directional model, we also characterize the performance benefits of using mMIMO in such a spectrum sharing network.
Doctor of Philosophy
The emergence of cloud-based video and audio streaming services, online gaming platforms, instantaneous sharing of multimedia contents (e.g., photos, videos) through social networking platforms, and virtual collaborative workspace/meetings require the cellular communication networks to provide high data-rate as well as reliable and ubiquitous connectivity. These constantly evolving requirements can be met by designing a wireless network that harmoniously exploits the symbiotic co-existence among different types of cutting-edge wireless technologies. One such technology is massive multiple-input multiple-output (mMIMO), whose core idea is to equip the cellular base stations (BSs) with a large number of antennas that can be leveraged through appropriate signal processing algorithms to simultaneously accommodate multiple users with reduced network interference. For successful deployment of mMIMO in the upcoming cellular standards, i.e., fifth-generation (5G) and beyond systems, it is necessary to characterize its performance in a large-scale wireless network taking into account the inherent spatial randomness in the BS and user locations. To achieve this goal, in this dissertation, we propose different statistical methods for the performance analysis of mMIMO networks using tools from stochastic geometry, which is a field of mathematics related to the study of random patterns of points. One of the major deployment issues of mMIMO systems is pilot contamination, which is a form of coherent network interference that degrades user performance. The main reason behind pilot contamination is the reuse of pilot sequences, which are a finite number of known signal waveforms used for channel estimation between a user and its serving BS. Further, the effect of pilot contamination is more severe for the cell-edge users, which are farther from their own BSs. An efficient scheme to mitigate the effect of pilot contamination is fractional pilot reuse (FPR). However, the efficiency of this scheme depends on the pilot partitioning rule that decides the fraction of total pilot sequences that should be used by the cell-edge users. Using appropriate statistical constructs from the stochastic geometry literature, such as Johnson-Mehl cells, we present a partitioning rule for efficient implementation of the FPR scheme in a cellular mMIMO network. Next, we focus on the performance analysis of the cell-free mMIMO network. In contrast to the cellular network, where each user is served by a single BS, in a cell-free network each user can be served by multiple access points (APs), which have less complex hardware compared to a BS. Owing to this cooperative and distributed implementation, there are no cell-edge users. Similar to the cellular counterpart, the cell-free systems also suffer from pilot contamination due to the reuse of pilot sequences throughout the network. Inspired by a hardcore point process known as the random sequential adsorption (RSA) process, we develop a new distributed pilot assignment algorithm that mitigates the effect of pilot contamination by ensuring a minimum distance among the co-pilot users. Further, we show that the performance of this distributed pilot assignment scheme is appreciable compared to different centralized pilot assignment schemes, which are algorithmically more complex and difficult to implement in a network. Moreover, this pilot assignment scheme leads to the construction of a new point process, namely the multilayer RSA process. We derive the statistical properties of this point process both in one and two-dimensional spaces. Further, in a cell-free mMIMO network, the APs are connected to a centralized baseband unit (BBU) that performs the bulk of the signal processing operations through finite capacity links, such as fiber optic cables. Apart from pilot contamination, another implementational issue associated with the cell-free mMIMO systems is the finite capacity of fronthaul links that results in user performance degradation. Using appropriate stochastic geometry-based tools, we model and analyze this network for two different implementation scenarios. In the first scenario, we consider a finite network where each AP serves all the users in the network. In the second scenario, we consider an infinite network where each user is served by a few nearby APs. As a consequence of this user-centric implementation, for each user, the BBU only needs to communicate with fewer APs thereby reducing information load on fronthaul links. From our analyses, we propose key guidelines for the deployment of both types of scenarios. The type of mMIMO systems that are discussed in this work will be operated in the sub-6 GHz frequency range of the electromagnetic spectrum. Owing to the limited availability of spectrum resources, usually, spectrum sharing is encouraged among different cellular operators in such bands. One such example is the citizen broadband radio service (CBRS) spectrum sharing systems proposed by the Federal Communications Commission (FCC). The final contribution of this dissertation focuses on the potential improvement that is possible by the use of mMIMO in the CBRS systems. As our first step, using tools from stochastic geometry, we model and analyze this system with a single antenna at the BSs. In our model, we take into account the key guidelines by the FCC for co-existence between licensed and unlicensed operators. Leveraging properties of the Poisson hole process and hardcore process, we provide useful theoretical expressions for different performance metrics such as medium access probability, coverage probability, and area spectral efficiency. These results are used to obtain system design guidelines for successful co-existence between these networks. We further highlight the potential improvement in the user performance with multiple antennas at the unlicensed BS.

We present the evolution of our ideas concerning the history of the Cosmos. They are based on Einstein’s theory of General Relativity in which E.P. Hubble and G. Lemaître brought two fundamental new concepts: the expansion of the Universe and the model of the Big Bang. They form the basic elements of the modern theory of Cosmology. We present very briefly the observational evidence which corroborates this picture based on a vast amount of data, among which the most recent ones come from the Planck mission with a detailed measurement of the cosmic microwave background (CMB) radiation. We show that during its evolution the Universe went through several phase transitions giving rise to the formation of particles, atoms, nuclei, etc. A particular phase transition, which occurred very early in the cosmic history, around 10–12 seconds after the Big Bang, is the Brout–Englert–Higgs (BEH) transition during which a fraction of the energy was transformed into mass, thus making it possible for most elementary particles to become massive.

Abstract In the induction room, the patient receives ECG and pulse oximetry monitoring while breathing oxygen via a clear facemask. Under local anaesthesia, venous access is gained with a 14 G (2 mm diameter) cannula and invasive arterial blood pressure monitoring is obtained via a 20 G (1 mm diameter) arterial cannula inserted into an artery, usually the radial artery. Two 14 G venous cannulas are inserted for surgery which may require massive blood transfusion. Central venous catheterization is necessary for the monitoring of right atrial filling pressure and the infusion of inotropes and vasopressors. The right internal jugular vein is usually used for catheterization because of its straight alignment with the superior vena cava. The left internal jugular and subclavian veins are acceptable alternatives if right internal jugular venous cannulation is difficult. If the ejection fraction is poor, a pulmonary artery catheter sheath can be inserted at the same time to facilitate the insertion of a pulmonary artery catheter. Unless the patient has an ejection fraction of less than 25 per cent, central venous catheterization can be performed after induction of anaesthesia. If the patient has angina, give sublingual or a nasal spray preparation of nitroglycerin.

Abstract The organist works from a very dififerent perspective to that of any of the individual pipes of his organ. Although in real organs the pipes themselves are often physically above the player, metaphorically speaking he surveys the keyboards and pedals from above, seeing patterns and musical forms that he constrains the instrument to follow. To play a piece on the organ is to call on many pipes simultaneously. In a complex piece, most of the pipes may at some point come into play. The organist must cause this massive apparatus to express its potential in an ordered way. These ordered patterns form a very tiny fraction of all the possible patterns that could be played, the great majority of which would be cacophonic.

This chapter focuses on supermassive black holes, which are sometimes abbreviated “SMBHs.” Stellar-mass black holes are clearly common consequences of stellar evolution, but they are not the only kinds of black holes identified by astronomers. Much more massive black holes are located in the center of many, and perhaps all, galaxies. These black holes are referred to as supermassive black holes. They are responsible for a range of phenomena originating from objects described as active galactic nuclei (AGN), which were first observed in the form of quasi-stellar objects (QSOs) or quasars. AGN are among the most luminous objects in the Universe and can be observed at great distances. The distances can be so great that the light travel time from the AGN to Earth is a large fraction of the age of the Universe. They are therefore often used to probe the evolution of the Universe.

Takotsubo syndrome is named after the octopus trap used by Japanese fisherman and reflects the shape of the left ventricle during systole in patients with this condition. Takotsubo is an acute cardiac syndrome (ACS), starting with chest pain, dyspnoea, ECG changes, sometimes presenting as STEMI or non-STEMI, and in some cases with hypotension, arrhythmias, pump failure, and sudden death. In most patients, the massive left ventricular dysfunction with a reduction in ejection fraction down to 35% is reversible over days, weeks, and months. However, around 4% of patients do not survive the acute condition. The mechanisms are thought to be neurological in nature, involving abnormalities of the amygdala and hippocampus of the mid-brain with over-activation of the sympathetic nervous and endothelin systems, leading to microvascular ischaemia and myocardial stunning. Treatment currently is not evidence-based, but for patients presenting in cardiogenic shock may involve left ventricular assist devices such as Impellla^R and ECMO (extra corporeal membrane oxygenation), as in apical ballooning inotropes may worsen the condition by creating a pressure gradient across the left ventricular outflow tract.

Abstract The reason to cover weapons of mass destruction in a book about extreme environments is because they have the potential to forever alter life on earth. The inconceivable destructive power of modern thermonuclear devices is antithetical to civilization, which requires a sophisticated infrastructure. The deaths from detonation of even one nuclear warhead over a population center would dwarf the September 11, 2001, World Trade Center disaster. The exploitation of fuel-loaded jets to attack the World Trade Center produced an unusual situation by trapping the victims inside the twin towers, whose collapse vaporized them. Usually, immediate deaths from massive explosions represent a fraction of the total, particularly if toxic gases or radioactivity are involved. The grim task is to separate those waiting to die from those who can recover with medical care. This principle of triage is similar for all types of weapons of mass destruction, whether they involve radioactivity, biological agents, or nerve gas. However, the problems of scale and loss of medical and transportation infrastructure to manage such disasters are seriously underestimated by triage strategies.

Abstract Recent liquidity assistance to failing savings and loans and banks (some insolvent and some large) in the U.S. and similar rescues abroad have prompted renewed interest in the topic of the lender of last resort. Under the classical doctrine, the need for a lender of last resort arises in a fractional reserve banking system when a banking panic, defmed as a massive scramble for high-powered money, threatens the money stock and, hence, the level of economic activity. The lender of last resort can allay an incipient panic by timely assurance that it will provide whatever high-powered money is required to satisfy the demand, either by offering liberal access to the discount window at a penalty rate or by open market purchases.

The trend towards sustainable development and the twin goals of reducing the carbon footprint using natural resources have put lignocellulosic residues in the spotlight as a feedstock for the development of biorefinery systems. These facts are compounded by the massive increase in the production of waste derived from the food supply chain, both agricultural and agri-food residues. Biorefineries are sustainable processing systems, encompassing a network of different processes and equipment, for the fractionation of biomass main components. These main fractions are then used to obtain new materials and high-added value products such as fuels and chemicals. This chapter presents the main industrial uses of agricultural and agri-food residues as part of the biorefinery. These industrial applications range from the most classical and widely studied, such as the papermaking industry and the production of fine chemicals, to the most novel applications in the food industry, the development of composite materials, clinical applications and for energy production, etc.

In an attempt to influence their pace of development, developing countries around the world try and influence the rate of investment (especially foreign private investments) in their economy. These countries attempt to influence investor decisions by matching and changing their portfolio with that of foreign investors’ needs. However, to make the country portfolio impressive, a country requires massive investment in infrastructure and other portfolio variables which brings countries at an impasse. This chapter discusses the viability of increasing income as a way out. This leads to another important issue as to how to increase revenue of a country with its limited portfolio of strengths. Recent developments in information technology and the Internet have led to a simple solution to this - offshore outsourcing. Outsourcing as a strategy has been around for many years. Traditionally, companies used to outsource their activities to independent suppliers who were best, but the choice was made from the suppliers located in the vicinity of the outsourcing company for easier coordination and control of the activities of the partner. However, due to developments in e-commerce, distance has become a relative term. Exchange of information in a fraction of a minute, irrespective of physical distance, has made it possible for companies to widen their horizons and look for independent suppliers in different nations — offshore outsourcing.

Abstract Pipe flows of bimodal settling slurries exhibit frictional head losses quite different from those determined simply as a sum of loss contributions by the individual fractions. Mechanisms governing flow friction and resulting from an interaction of grains of different fractions in transported slurry are not well understood. This makes a prediction of the frictional head loss in flows of bimodal slurries with Newtonian carrier uncertain. An extensive experimental campaign was conducted in GIW Hydraulic Laboratory in 2016 with slurries of four narrow graded fractions of the virtually same grain densities and very different grain sizes (carrier-liquid fraction, pseudo-homogeneous-, heterogeneous-, and stratified fractions). Besides testing of the individual fractions, different combinations of the fraction mixtures (bimodal, three- and four-component) were tested as well. In our previous work published in 2018, we employed experimental results for bimodal slurry composed of coarse granite rock (the stratified fraction) and fine sand (the pseudo-homogeneous fraction) to analyze the observed considerable reduction of the frictional head loss caused by an addition of the fine sand to the granite rock slurry. In this work, we extend our analysis to the other bimodal slurries composed of permutations of the four fractions (in total 3 additional bimodal slurries) with a major objective to identify possible mechanisms leading to a modification of the frictional head loss due to an addition of a finer fraction to a coarser mono-disperse slurry, and to quantify this effect for the purposes of a predictive four-component model (4CM). The investigation shows that the frictional loss of bimodal slurry is always smaller than the theoretical loss obtained as the sum of losses of the fractions, although the massive reduction observed in the slurry composed of the stratified rock and fine sand is not observed in any other bimodal slurry. The investigation also suggests that the friction effect obtained by the finer fraction addition is due to different mechanisms for different bimodal slurries although all mechanisms are associated with altering mechanical friction due to granular contacts. It is shown that the observed effects can be well reproduced by the friction loss model 4CM, calibrated by the experimental data set from the 203-mm pipe and validated by the data set from the 103-mm pipe.

Today's social platforms, such as Twitter and Facebook, continuously generate massive volumes of data. The resulting data streams exceed any reasonable limit for permanent storage, especially since data is often redundant, overlapping, sparse, and generally of low value. This calls for means to retain solely a small fraction of the data in an online manner. In this paper, we propose techniques to effectively decide which data to retain, such that the induced loss of information, the regret of neglecting certain data, is minimized. These techniques enable not only efficient processing of massive streaming data, but are also adaptive and address the dynamic nature of social media. Experiments on large-scale real-world datasets illustrate the feasibility of our approach in terms of both, runtime and information quality.

Exploration under glacial sediment cover is a necessary part of modern mineral exploration in Canada. Traditional indicator methods use visual examination to identify mineral grains in the 250 to 2000 µm fraction of till heavy-mineral concentrates (HMC). This study tests automated mineralogical methods using scanning electron microscopy to identify indicator minerals in the fine (&amp;lt;250 µm) HMC fraction of till. Automated mineralogy of polished grains from the fine HMC enables rapid data collection (10 000-300 000 grains/sample). Samples collected near two deposits were used to test this method: four from the upper-amphibolite facies Izok Lake volcanogenic massive-sulfide deposit, Nunavut, and five from the Sisson granite-hosted W-Mo deposit, New Brunswick. The less than 250 µm HMC fraction of till samples collected down ice of each deposit contain ore and alteration minerals typical of their deposit type. Sulfide minerals occur mainly as inclusions in oxidation-resistant minerals, including minerals previously identified in each deposit's metamorphic alteration halo, and are found to occur farther down ice than the grains identified visually in the greater than 250 µm HMC fraction. This project's workflow expands the detectable footprint for certain indicator minerals and enhances the information that can be collected from till samples.

As we move away from a fossil fuel-driven economy, the demand for metals used in energy-dense, rechargeable batteries is increasing; these include cobalt and lithium. Although cobalt is mostly obtained as a by-product from nickel and copper mining, significant amounts also occur in volcanogenic massive sulfide (VMS) deposits, of which Canada has many. However, the primary controls on cobalt distribution in VMS deposits are poorly understood, and may be affected by deformation and metamorphism. We show that cobalt can occur in pyrite, which retains its primary composition through greenschist facies metamorphism; and in pyrrhotite, which expels some cobalt during deformation to form cobaltite crystals. In contrast, most of the global lithium supply is derived from rare metal pegmatites and salars, with pegmatites the most important Canadian source. Our preliminary results confirm that lithium-bearing pegmatites can form directly during anatexis, as well as from fractional crystallization of large bodies of granitic magma.