Universality of the muon component of extensive air showers

In extensive air shower experiments, the number of muons crossing a detector at a given position, as well as their arrival time, arrival direction, and energy, are determined by a more fundamental 3-dimensional distribution linked to the hadronic core of the shower. Muons are produced high up in the atmosphere after the decay of mesons in the hadronic cascade. The distributions of production depth, energy, and transverse momentum of muons are enough to fully predict the muon component of air showers in any particular observational condition. By using air-shower simulations with the state-of-the-art hadronic interaction models, the mentioned distributions at production are analyzed as a function of zenith angle, primary mass, and hadronic interaction model, and their level of universality is studied and assessed in an exhaustive manner for the first time

Rigorous asymptotics of traveling-wave solutions to the thin-film equation and Tanner's law

We are interested in traveling-wave solutions to the thin-film equation with zero microscopic contact angle (in the sense of complete wetting without precursor) and inhomogeneous mobility with slippage exponent n ∈ (3/2,7/3). Existence and uniqueness of these solutions have been established by Maria Chiricotto and the first of the authors in previous work under the assumption of subquadratic growth as h → ∞. In the present work we investigate the asymptotics of solutions as h → 0 (the contact-line region) and h → ∞. As h → 0 we observe, to leading order, the same asymptotics as for traveling waves or source-type self-similar solutions to the thin-film equation  with homogeneous mobility and we additionally characterize corrections to this law. Moreover, as h → ∞ we identify, to leading order, the logarithmic Tanner profile, i.e. the solution to the corresponding homogeneous problem that determines the apparent macroscopic contact angle. Besides higher-order terms, corrections turn out to affect the asymptotic law as h → ∞ only by setting the length scale in the logarithmic Tanner profile. Moreover, we prove that both the correction and the length scale depend smoothly on n. Hence, in line with the common philosophy, the precise modeling of liquid–solid interactions (within our model, the mobility exponent) does not affect the qualitative macroscopic properties of the film

Immigration and the top 1 percent

Using administrative data on the universe of UK taxpayers, we study the contribution of migrants to the rise in UK top incomes. We show migrants are over-represented at the top of the income distribution, with migrants twice as prevalent in the top 0.01% as anywhere in the bottom 97%. These high incomes are predominantly from labour, rather than capital, and migrants are concentrated in only a handful of industries, predominantly finance. Almost all (90%) of the observed growth in the UK top 1% income share over the past 20 years has accrued to migrants

Importing inequality: immigration and the top 1 percent

In this paper we study the contribution of migrants to the rise in UK top incomes. Using administrative data on the universe of UK taxpayers we show migrants are over-represented at the top of the income distribution, with mi-grants twice as prevalent in the top 0.1% as anywhere in the bottom 97%. These high incomes are predominantly from labour, rather than capital, and migrants are concentrated in only a handful of industries, predominantly finance. Almost all (85%) of the growth in the UK top 1% income share over the past 20 years can be attributed to migration

An XMM-Newton and NuSTAR study of IGR J18214-1318: a non-pulsating high-mass X-ray binary with a neutron star

IGR J18214-1318, a Galactic source discovered by the International Gamma-Ray Astrophysics Laboratory, is a high-mass X-ray binary (HMXB) with a supergiant O-type stellar donor. We report on the XMM-Newton and NuSTAR observations that were undertaken to determine the nature of the compact object in this system. This source exhibits high levels of aperiodic variability, but no periodic pulsations are detected with a 90% confidence upper limit of 2% fractional rms between 0.00003-88 Hz, a frequency range that includes the typical pulse periods of neutron stars (NSs) in HMXBs (0.1-10$^3$ s). Although the lack of pulsations prevents us from definitively identifying the compact object in IGR J18214-1318, the presence of an exponential cutoff with e-folding energy $\lesssim30$ keV in its 0.3-79 keV spectrum strongly suggests that the compact object is an NS. The X-ray spectrum also shows a Fe K$\alpha$ emission line and a soft excess, which can be accounted for by either a partial-covering absorber with $N_{\mathrm{H}}\approx10^{23}$ cm$^{-2}$ which could be due to the inhomogeneous supergiant wind, or a blackbody component with $kT=1.74^{+0.04}_{-0.05}$ keV and $R_{BB}\approx0.3$ km, which may originate from NS hot spots. Although neither explanation for the soft excess can be excluded, the former is more consistent with the properties observed in other supergiant HMXBs. We compare IGR J18214-1318 to other HMXBs that lack pulsations or have long pulsation periods beyond the range covered by our observations.Comment: 15 pages, 12 figures, 4 table

The effect of Electro Spark Deposition on the microstructure and mechanical properties of IN718

The Electro Spark Deposition is a technique of continuing interest to repair or coat the surface of expensive components used in the aerospace industry. A potential use for this technique is to repair damaged turbine blades made with nickel-based superalloys, such as IN718. Nickel-based superalloys are susceptible to hot cracking and post weld heat treatment cracking during conventional processes, due to the high heat input that contributes to issues mainly observed in the heat affected zone of the components. An interesting approach to reduce thermal issues in nickel-based superalloys is to reduce the heat input during welding or posterior treatments. In this case, the use of the ESD technique to repair expensive parts made with nickel-based superalloys is a possibility, since this process has the advantage to generate minimal heat input onto the substrate. In order to better understand the inherent defects of this method and the microstructure and properties achieved through the ESD process, a systematic study of the effects of the main variables in this process is a necessity, including but not limited to the voltage, capacitance and spark frequency. In this work, IN718 deposited using ESD with different pulse energy and frequency, achieved by varying the voltage, capacitance and pulse frequency, was systematically investigated in terms of its microstructure, microhardness and tensile properties. It has been observed that the increasing pulse energy and frequency in the ESD process promotes the formation of internal voids and intermetallic phases that may be undesirable in the process of repairing or coating of components. The presence of intermetallic phases in a certain amount and distribution is believed to increase the susceptibility for cracking of the deposited layers. Tensile samples repaired with conditions that present less internal defects showed ductility closer to the ductility observed for the parent material

Probing the π0\pi^0 spectrum at high-xx in proton-Air interactions at ultra-high energies

The average number of muons in air showers and its connection with shower development has been studied extensively in the past. With the upcoming detector upgrades, UHECR observatories will be able to probe higher moments of the distribution of the number of muons. Here a study of the physics of the fluctuations of the muon content is presented. In addition to proving that the fluctuations must be dominated by the first interactions, we show that low-$N_{\mu}$ tail of the shower-to-shower distribution of the number of muons is determined by the high-$x_{\rm L}$ region of the production cross-section of neutral pions in the first interaction.Comment: Proceedings of Ultra High Energy Cosmic Rays 201