Characterization of nanoparticles generated from drilling activities within a sub-surface mine using a novel sampler

2020 Spring.Includes bibliographical references.This study employed nanoparticle sampling techniques to characterize the aerosol generated from a routine mining activity. A preliminary survey of the particle emission from the feed-leg drilling activity was conducted in the excavations of an experimental mine. The level of particulate exposure was sampled using a novel sampler for respirable and nanometer sized particles; and monitored by direct reading real time instruments. A NanoScan scanning mobility particle sizer (measurement range 10-420 nm) and an optical particle sizer (measurement range 0.3-10 µm) were used. Particulate morphological and structural examination of samples collected with the novel nanoparticle sampler and a thermophoretic sampler was conducted through transmission and scanning electron microscopy and x-ray dispersive analysis. Based on the real-time instrument data, the researchers found high concentrations (> 3.5 x 106 particles/cm3) of ultrafine/nanoparticles generated from the drilling activity. A large amount of submicron silica, spherical primary and agglomerated particles rich in carbon were discovered via analysis of particle sampler specimens with energy-dispersive x-ray spectroscopy. Many particle agglomerates contained primary particles less than 100 nm. Exposure to particles in the nanometer size from various sources within the mining environment has not been well characterized and may be associated with respiratory and systemic disease among miners

Numerical determination of entanglement entropy for a sphere

We apply Srednicki's regularization to extract the logarithmic term in the entanglement entropy produced by tracing out a real, massless, scalar field inside a three dimensional sphere in 3+1 flat spacetime. We find numerically that the coefficient of the logarithm is -1/90 to 0.2 percent accuracy, in agreement with an existing analytical result

Heterotic flux backgrounds and their IIA duals

We study four-dimensional heterotic flux vacua with N=2 spacetime supersymmetry. A worldsheet perspective is used to clarify quantization conditions associated to the fluxes and the constraints these place on the moduli spaces of resulting compactifications. We propose that these vacua fit naturally in the context of heterotic/IIA duality as heterotic duals to compactifications on K3-fibered but not elliptically fibered Calabi-Yau three-folds. We present some examples of such potential dual pairs

Off-shell superconformal higher spin multiplets in four dimensions

We formulate off-shell N=1 superconformal higher spin multiplets in four spacetime dimensions and briefly discuss their coupling to conformal supergravity. As an example, we explicitly work out the coupling of the superconformal gravitino multiplet to conformal supergravity. The corresponding action is super-Weyl invariant for arbitrary supergravity backgrounds. However, it is gauge invariant only if the supersymmetric Bach tensor vanishes. This is similar to linearised conformal supergravity in curved background

Higher Spin Black Holes in Three Dimensions: Comments on Asymptotics and Regularity

In the context of (2+1)--dimensional SL(N,R)\times SL(N,R) Chern-Simons theory we explore issues related to regularity and asymptotics on the solid torus, for stationary and circularly symmetric solutions. We display and solve all necessary conditions to ensure a regular metric and metric-like higher spin fields. We prove that holonomy conditions are necessary but not sufficient conditions to ensure regularity, and that Hawking conditions do not necessarily follow from them. Finally we give a general proof that once the chemical potentials are turn on -- as demanded by regularity -- the asymptotics cannot be that of Brown-Henneaux

Criminal Law and Procedure

The authors have endeavored to select from the many cases and bills those that have the most significant practical impact on the daily practice of criminal law in the Commonwealth. Due to space constraints, the authors have stayed away from discussing settled principles, with a focus on the take away for a particular case

On Higher Spin Symmetries in AdS_{5}

A special embedding of the SU(4) algebra in SU(10), including both spin two and spin three symmetry generators, is constructed. A possible five dimensional action for massless spin two and three fields with cubic interaction is constructed. The connection with the previously investigated higher spin theories in $AdS_{5}$ background is discussed. Generalization to the more general case of symmetries, including spins $2,3,\dots s$, is shown.Comment: 24 pages, Latex, v.2, minor corrections, references added, v.3, revised version, accepted for publication in JHE