Interdependent Formation of Symbolic and Regulatory Boundaries: The Discursive Contestation Around the Home-Sharing Category

The formation of boundaries between established and emergent categories is a complex social process. Therein, our understanding of how symbolic boundaries translate into regulatory boundaries is underdeveloped. Extant research either treats laws and regulations for categories as given, or it assumes a seamless translation of a symbolic into a regulatory boundary. This sidelines that market participants actively contest and shape boundaries between categories. To address this lacuna, we open the black box of how symbolic boundaries are translated into regulatory boundaries. We adopt a discursive perspective and conduct a longitudinal study of the contestation around the categories of home sharing and short-term rental in Europe. Our analysis shows how symbolic and regulatory boundaries are formed in a causal sequential process, driven by shifts in the field positioning of market actors and in the discursive accounts they mobilize. We develop a theoretical model of the discursive foundation of category boundary formation. At the heart of our theorization are discursive accounts and how shifting coalitions of market participants mobilize them to shape the evolving symbolic and regulatory boundaries between an emergent and an established category. We contribute to category research by unearthing the interdependent formation of symbolic and regulatory boundaries and the role of discursive accounts in these processes

Interdependent Formation of Symbolic and Regulatory Boundaries: The Discursive Contestation Around the Home-Sharing Category

The formation of boundaries between established and emergent categories is a complex social process. Therein, our understanding of how symbolic boundaries translate into regulatory boundaries is underdeveloped. Extant research either treats laws and regulations for categories as given or assumes a seamless translation of a symbolic into a regulatory boundary. This sidelines that market participants actively contest and shape boundaries between categories. To address this lacuna, we open the black box of how symbolic boundaries are translated into regulatory boundaries. We adopt a discursive perspective and conduct a longitudinal study of the contestation around the categories of home sharing and short-term rental in Europe. Our analysis shows how symbolic and regulatory boundaries are formed in a causal sequential process, driven by shifts in the field positioning of market actors and in the discursive accounts they mobilize. We develop a theoretical model of the discursive foundation of category boundary formation. At the heart of our theorization are discursive accounts and how shifting coalitions of market participants mobilize them to shape the evolving symbolic and regulatory boundaries between an emergent and an established category. We contribute to category research by unearthing the interdependent formation of symbolic and regulatory boundaries and the role of discursive accounts in these processes

Laser polishing of niobium for superconducting radio-frequency accelerator applications

Interior surfaces of niobium cavities used in superconducting radio frequency accelerators are now obtained by buffered chemical polish and/or electropolish. Laser polishing is a potential alternative, having advantages of speed, freedom from noxious chemistry and availability of in-process inspection. We studied the influence of the laser power density and laser beam raster rate on the surface topography. These two factors need to be combined carefully to smooth the surface without damage. Computational modeling was used to estimate the surface temperature and gain insight into the mechanism of laser polishing. Power spectral density analysis of surface topography measurements shows that laser polishing can produce smooth topography similar to that obtained by electropolish. This is a necessary first step toward introducing laser polishing as an alternative to the currently practiced chemical polishing

The Contribution of Microbunching Instability to Solar Flare Emission in the GHz to THz Range of Frequencies

Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed double spectra. Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible

Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD) and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes

Twenty-seventh Annual Bibliography, 2013 (Contemporary German Literature Collection)

Bibliography of contemporary German literature volumes added the previous year to Washington University Libraries\u27 Contemporary German Literature Collection. These acquisitions generally include novels, poetry, short story collections, essays, autobiographical works, and literary and cultural periodicals from publishers in Germany, Austria, and Switzerland. This Collection serves as the research arm for the Department of Germanic Languages and Literature\u27s Max Kade Center for Contemporary German Literature. This bibliography is compiled by Washington University\u27s Department of Germanic Languages and Literatures in cooperation with the University Libraries. See also Contemporary German Literature Collection and Max Kade Center for Contemporary German Literature

Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay

In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Non-zero scalar or tensor interactions would imply an additional contribution to the differential decay rate of the neutron, the Fierz interference term. We derive a limit on this hypothetical term from a measurement using spin polarized neutrons. This method is statistically less sensitive than the determination from the spectral shape but features much cleaner systematics. We obtain a limit of b = 0.017(21) at 68.27 C.L., improving the previous best limit from neutron decay by a factor of four.Comment: Phys. Rev. Lett., https://journals.aps.org/prl

Design of the Magnet System of the Neutron Decay Facility PERC

The PERC (Proton and Electron Radiation Channel) facility is currently under construction at the research reactor FRM II, Garching. It will serve as an intense and clean source of electrons and protons from neutron beta decay for precision studies. It aims to contribute to the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing element $V_{ud}$ from neutron decay data and to search for new physics via new effective couplings. PERC's central component is a 12m long superconducting magnet system. It hosts an 8m long decay region in a uniform field. An additional high-field region selects the phase space of electrons and protons which can reach the detectors and largely improves systematic uncertainties. We discuss the design of the magnet system and the resulting properties of the magnetic field.Comment: Proceedings of the International Workshop on Particle Physics at Neutron Sources PPNS 2018, Grenoble, France, May 24-26, 201