Entrepreneurship through acquisition: a study on self-funded search funds

This paper is the first and so far only study on self-funded search funds which is an emerging alternative to the traditional search fund model. The study collects and evaluates primary qualitative data from first-time self-funded searchers. Based on the survey results, self-funded search funds have a shorter search phase, acquire smaller companies by using more debt, and achieve a higher return on invested capital (ROI) and internal rate of return (IRR)than traditional search funds. The evidence presented suggests that searchers decide for a self-funded search because of favorable deal terms at acquisition, more decision-making power and flexibility in acquiring and operating the target company

Hybrid waveguide-bulk multi-path interferometer with switchable amplitude and phase

We design and realise a hybrid interferometer consisting of three paths based on integrated as well as on bulk optical components. This hybrid construction offers a good compromise between stability and footprint on one side and means of intervention on the other. As experimentally verified by the absence of higher-order interferences, amplitude and phase can be manipulated in all paths independently. In conjunction with single photons, the setup can, therefore, be applied for fundamental investigations on quantum mechanics.Comment: accepted in APL Photonic

Healthy Worker Survivor Bias in a Cohort of Uranium Miners from the Colorado Plateau

Radon, a ubiquitous gas present in breathing air and concentrated in the indoor environment, is a well established risk factor for lung cancer. Primarily, evidence for this association originated in studies of miners occupationally exposed to high con- centrations of radon. Much work has been done to predict lung cancer risk due to lower dose exposures in residences using dose-response curves derived from long- term, high-dose miner studies and shorter-term, low-dose residential studies. While residential studies suffer from a high probability of exposure misclassification at low exposures, miner studies present an opportunity to apply more precise estimates of the lung cancer-radon association to risk assessments. However, potential bias due to the Healthy Worker survivor bias has not been addressed in previous studies of occupa- tional exposure to radon. The Healthy Worker survivor bias occurs when workers with poor prognosis leave work sooner than those with better prognosis, thus creating an apparent association between low cumulative occupational exposures and mortality. Healthy worker survivor bias has been shown to substantially bias dose-response esti- mates in other settings, but it has not been explored in occupational studies of radon exposure. We apply two g-methods designed for addressing healthy worker survivor bias that cannot be controlled using conventional statistical methods. We utilize data from the Colorado Plateau uranium miners cohort, which comprises 4,137 male ura- nium miners who agreed to participate in a health study between 1950 and 1960 and were followed up for mortality through 2005. Our results suggest that there may be healthy worker survivor bias of the association between cumulative radon exposure and both lung cancer and all cause mortality. This work highlights the need for non- standard approaches to controlling time-varying confounding in occupational data. We show that, under certain conditions, g-methods can control this confounding, but that careful consideration should be made in the choice of method.Doctor of Philosoph

Neural Microfacet Fields for Inverse Rendering

We present Neural Microfacet Fields, a method for recovering materials, geometry, and environment illumination from images of a scene. Our method uses a microfacet reflectance model within a volumetric setting by treating each sample along the ray as a (potentially non-opaque) surface. Using surface-based Monte Carlo rendering in a volumetric setting enables our method to perform inverse rendering efficiently by combining decades of research in surface-based light transport with recent advances in volume rendering for view synthesis. Our approach outperforms prior work in inverse rendering, capturing high fidelity geometry and high frequency illumination details; its novel view synthesis results are on par with state-of-the-art methods that do not recover illumination or materials.Comment: Project page: https://half-potato.gitlab.io/posts/nmf

Geometric potential and transport in photonic topological crystals

We report on the experimental realization of an optical analogue of a quantum geometric potential for light wave packets constrained on thin dielectric guiding layers fabricated in silica by the femtosecond laser writing technology. We further demonstrate the optical version of a topological crystal, with the observation of Bloch oscillations and Zener tunneling of purely geometric nature

Inhalation Exposures to Particulate Matter and Carbon Monoxide during Ethiopian Coffee Ceremonies in Addis Ababa: A Pilot Study

The unique Ethiopian cultural tradition of the coffee ceremony increases inhalation exposures to combustion byproducts. This pilot study evaluated exposures to particulate matter and carbon monoxide in ten Addis Ababa homes during coffee ceremonies. For coffee preparers the geometric mean (57 μg/m3) and median (72 μg/m3) contributions to an increase in a 24-hour time-weighted average exposure were above World Health Organization (WHO) guidelines. At 40% of the study sites the contribution to the 24-hour average exposure was greater than twice the WHO guideline. Similar exposure increases existed for ceremony participants. Particulate matter concentrations may be related to the use of incense during the ceremony. In nearly all homes the WHO guideline for a 60-minute exposure to carbon monoxide was exceeded. Finding control measures to reduce these exposures will be challenging due to the deeply engrained nature of this cultural practice and the lack of availability of alternative fuels

Identifying and estimating effects of sustained interventions under parallel trends assumptions

Many research questions in public health and medicine concern sustained interventions in populations defined by substantive priorities. Existing methods to answer such questions typically require a measured covariate set sufficient to control confounding, which can be questionable in observational studies. Differences-in-differences relies instead on the parallel trends assumption, allowing for some types of time-invariant unmeasured confounding. However, most existing difference-in-differences implementations are limited to point treatments in restricted subpopulations. We derive identification results for population effects of sustained treatments under parallel trends assumptions. In particular, in settings where all individuals begin follow-up with exposure status consistent with the treatment plan of interest but may deviate at later times, a version of Robins' g-formula identifies the intervention-specific mean under SUTVA, positivity, and parallel trends. We develop consistent asymptotically normal estimators based on inverse-probability weighting, outcome regression, and a double robust estimator based on targeted maximum likelihood. Simulation studies confirm theoretical results and support the use of the proposed estimators at realistic sample sizes. As an example, the methods are used to estimate the effect of a hypothetical federal stay-at-home order on all-cause mortality during the COVID-19 pandemic in spring 2020 in the United States.Comment: 15 pages, 2 figure

Self-Calibration of Neutrino Detectors using characteristic Backgrounds

We introduce the possibility to use characteristic natural neutrino backgrounds, such as Geoneutrinos (\bar{\nu}_e) or solar neutrinos (\nu_e), with known spectral shape for the energy calibration of future neutrino detectors, e.g. Large Liquid Scintillator Detectors. This "CalEffect" could be used without the need to apply any modifications to the experiment in all situations where one has a suitable background with sufficient statistics. After deriving the effect analytically using \chi^2 statistics, we show that it is only tiny for reactor neutrino experiments, but can be applicable in other situations. As an example, we present its impact on the identification of the wiggles in the power spectrum of supernova neutrinos caused by Earth matter effects. The Self-Calibration Effect could be used for cross checking other calibration methods and to resolve systematical effects in the primary neutrino interaction processes, in particular in the low energy cross sections.Comment: 6 pages, 4 figure