On the Toxicity of the Urine:

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The Role of Nonlinear Dynamics in Quantitative Atomic Force Microscopy

Various methods of force measurement with the Atomic Force Microscope (AFM) are compared for their ability to accurately determine the tip-surface force from analysis of the nonlinear cantilever motion. It is explained how intermodulation, or the frequency mixing of multiple drive tones by the nonlinear tip-surface force, can be used to concentrate the nonlinear motion in a narrow band of frequency near the cantilevers fundamental resonance, where accuracy and sensitivity of force measurement are greatest. Two different methods for reconstructing tip-surface forces from intermodulation spectra are explained. The reconstruction of both conservative and dissipative tip-surface interactions from intermodulation spectra are demonstrated on simulated data.Comment: 25 pages (preprint, double space) 7 figure

Unconfined Aquifer Flow Theory - from Dupuit to present

Analytic and semi-analytic solution are often used by researchers and practicioners to estimate aquifer parameters from unconfined aquifer pumping tests. The non-linearities associated with unconfined (i.e., water table) aquifer tests makes their analysis more complex than confined tests. Although analytical solutions for unconfined flow began in the mid-1800s with Dupuit, Thiem was possibly the first to use them to estimate aquifer parameters from pumping tests in the early 1900s. In the 1950s, Boulton developed the first transient well test solution specialized to unconfined flow. By the 1970s Neuman had developed solutions considering both primary transient storage mechanisms (confined storage and delayed yield) without non-physical fitting parameters. In the last decade, research into developing unconfined aquifer test solutions has mostly focused on explicitly coupling the aquifer with the linearized vadose zone. Despite the many advanced solution methods available, there still exists a need for realism to accurately simulate real-world aquifer tests

On the stability and uniqueness of the flow of a fluid through a porous medium

© 2016, The Author(s). In this short note, we study the stability of flows of a fluid through porous media that satisfies a generalization of Brinkman’s equation to include inertial effects. Such flows could have relevance to enhanced oil recovery and also to the flow of dense liquids through porous media. In any event, one cannot ignore the fact that flows through porous media are inherently unsteady, and thus, at least a part of the inertial term needs to be retained in many situations. We study the stability of the rest state and find it to be asymptotically stable. Next, we study the stability of a base flow and find that the flow is asymptotically stable, provided the base flow is sufficiently slow. Finally, we establish results concerning the uniqueness of the flow under appropriate conditions, and present some corresponding numerical results

Syndromics: A Bioinformatics Approach for Neurotrauma Research

Substantial scientific progress has been made in the past 50 years in delineating many of the biological mechanisms involved in the primary and secondary injuries following trauma to the spinal cord and brain. These advances have highlighted numerous potential therapeutic approaches that may help restore function after injury. Despite these advances, bench-to-bedside translation has remained elusive. Translational testing of novel therapies requires standardized measures of function for comparison across different laboratories, paradigms, and species. Although numerous functional assessments have been developed in animal models, it remains unclear how to best integrate this information to describe the complete translational “syndrome” produced by neurotrauma. The present paper describes a multivariate statistical framework for integrating diverse neurotrauma data and reviews the few papers to date that have taken an information-intensive approach for basic neurotrauma research. We argue that these papers can be described as the seminal works of a new field that we call “syndromics”, which aim to apply informatics tools to disease models to characterize the full set of mechanistic inter-relationships from multi-scale data. In the future, centralized databases of raw neurotrauma data will enable better syndromic approaches and aid future translational research, leading to more efficient testing regimens and more clinically relevant findings

Competition and Market Strategies in the Swiss Fixed Telephony Market. An estimation of Swisscom’s dynamic residual demand curve.

Fixed telephony has long been a fundamentally important market for European telecommunications operators. The liberalisation and the introduction of regulation in the end of the 1990s, however, allowed new entrants to compete with incumbents at the retail level. A rapid price decline and a decline in revenues followed. Increased retail competition consequently led a number of national regulators to deregulate this market. In 2013, however, many European countries (including Switzerland) continued to have partially binding retail price regulation. More than a decade after liberalisation and the introduction of wholesale and retail price regulation, sufficient data is available to empirically measure the success of regulation and assess its continued necessity. This paper develops a market model based on a generalised version of the traditional “dominant firm – competitive fringe” model allowing the incumbent also more competitive conduct than that of a dominant firm. A system of simultaneous equations is developed and direct estimation of the incumbent‟s residual demand function is performed by instrumenting the market price by incumbent-specific cost shifting variables as well as other variables. Unlike earlier papers that assess market power in this market, this paper also adjusts the market model to ensure a sufficient level of cointegration and avoid spurious regression results. This necessitates introducing intertemporal effects. While the incumbent's conduct cannot be directly estimated using this framework, the concrete estimates show that residual demand is inelastic (long run price elasticity of residual demand of -0.12). Such a level of elasticity is, however, only compatible with a profit maximising incumbent in the case of largely competitive conduct (conduct parameter below 0.12 and therefore close to zero). It is therefore found that the Swiss incumbent acted rather competitively in the fixed telephony retail market in the period under review (2004-2012) and that (partial) retail price caps in place can no longer be justified on the basis of a lack of competition