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Search Results: 1 - 10 of 28351 matches for " Martin Mueller "
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Model of surface instabilities induced by stress
Judith Mueller,Martin Grant
Physics , 1998, DOI: 10.1103/PhysRevLett.82.1736
Abstract: We propose a model based on a Ginzburg-Landau approach to study a strain relief mechanism at a free interface of a non-hydrostatically stressed solid, commonly observed in thin-film growth. The evolving instability, known as the Grinfeld instability, is studied numerically in two and three dimensions. Inherent in the description is the proper treatment of nonlinearities. We find these nonlinearities can lead to competitive coarsening of interfacial structures, corresponding to different wavenumbers, as strain is relieved. We suggest ways to experimentally measure this coarsening.
Weak subsumption Constraints for Type Diagnosis: An Incremental Algorithm
Martin Mueller,Joachim Niehren
Computer Science , 1995,
Abstract: We introduce constraints necessary for type checking a higher-order concurrent constraint language, and solve them with an incremental algorithm. Our constraint system extends rational unification by constraints x$\subseteq$ y saying that ``$x$ has at least the structure of $y$'', modelled by a weak instance relation between trees. This notion of instance has been carefully chosen to be weaker than the usual one which renders semi-unification undecidable. Semi-unification has more than once served to link unification problems arising from type inference and those considered in computational linguistics. Just as polymorphic recursion corresponds to subsumption through the semi-unification problem, our type constraint problem corresponds to weak subsumption of feature graphs in linguistics. The decidability problem for \WhatsIt for feature graphs has been settled by D\"orre~\cite{Doerre:WeakSubsumption:94}. \nocite{RuppRosnerJohnson:94} In contrast to D\"orre's, our algorithm is fully incremental and does not refer to finite state automata. Our algorithm also is a lot more flexible. It allows a number of extensions (records, sorts, disjunctive types, type declarations, and others) which make it suitable for type inference of a full-fledged programming language.
How paper folds: bending with local constraints
Jemal Guven,Martin Michael Mueller
Physics , 2007, DOI: 10.1088/1751-8113/41/5/055203
Abstract: A variational framework is introduced to describe how a surface bends when it is subject to local constraints on its geometry. This framework is applied to describe the patterns of a folded sheet of paper. The unstretchability of paper implies a constraint on the surface metric; bending is penalized by an energy quadratic in mean curvature. The local Lagrange multipliers enforcing the constraint are identified with a conserved tangential stress that couples to the extrinsic curvature of the sheet. The framework is illustrated by examining the deformation of a flat sheet into a generalized cone.
Exploring the possibility of detecting dark energy in a terrestrial experiment using atom interferometry
Martin L. Perl,Holger Mueller
Physics , 2010,
Abstract: The majority of astronomers and physicists accept the reality of dark energy but also believe it can only be studied indirectly through observation of the motions of galaxies. This paper opens the experimental question of whether it is possible to directly detect dark energy on earth using atom interferometry through a force hypothetically caused by a gradient in the dark energy density. Our proposed experimental design is outlined. The possibility of detecting other weak fields is briefly discussed.
Investigation of the Galactic Magnetic Field with Ultra-High Energy Cosmic Rays
Martin Erdmann,Gero Mueller,Martin Urban
Physics , 2015,
Abstract: We present a method to correct for deflections of ultra-high energy cosmic rays in the galactic magnetic field. We perform these corrections by simulating the expected arrival directions of protons using a parameterization of the field derived from Faraday rotation and synchrotron emission measurements. To evaluate the method we introduce a simulated astrophysical scenario and two observables designed for testing cosmic ray deflections. We show that protons can be identified by taking advantage of the galactic magnetic field pattern. Consequently, cosmic ray deflection in the galactic field can be verified experimentally. The method also enables searches for directional correlations of cosmic rays with source candidates.
Sonographically guided lymph node biopsy: Complication rates  [PDF]
Michael Mueller, Genia Wittich, Suemeyra Oeztuerk, Wolfgang Kratzer, Mark Martin Haenle, Richard Andrew Mason
Open Journal of Clinical Diagnostics (OJCD) , 2012, DOI: 10.4236/ojcd.2012.22006
Abstract: Purpose: The study investigated the rate of complications associated with sonographically guided lymph node biopsies and assessed potential risk factors. Methods: A total of 536 sonographically guided puncture procedures (283 males, 52.8%; 253 females, 47.2%; average age 57.0 ± 16.0 years; range 14 - 87 years) were performed in 469 patients for the work-up of unclear lymphadenopathy. Events, complications and potential risk factors, were prospectively documented. Results: The 469 patients underwent a total of 536 puncture procedures (PP) including 663 punctures and 1485 passes. Lymph node localizations were intraabdominal (55.2%, n = 296), cervical (22.4%, n = 120), inguinal (12.9%, n = 69), axillary (7.8%, n = 42) and other (1.7%, n = 9). No complications were documented during the entire study period. There was no increased risk of complications documented for the potential risk factors number of punctures, the number of passes, the localization, diameter of the lymph node (s), puncture technique, needle gauge, as well as patients’ sex, age and coagulation parameters, and the experience of the examiner. Conclusions: Our findings confirm the safety of percutaneous sonographically guided lymph node biopsies in different regions of the body in patients with adequate coagulation parameters undergoing pre-interventional color Doppler ultrasound examination.
The Design of Networked Exertion Games
Florian 'Floyd' Mueller,Frank Vetere,Martin Gibbs
Journal of Virtual Reality and Broadcasting , 2009,
Abstract: Incorporating physical activity and exertion into pervasive gaming applications can provide health and social benefits. Prior research has resulted in several prototypes of pervasive games that encourage exertion as interaction form; however, no detailed critical account of the various approaches exists. We focus on networked exertion games and detail some of our work while identifying the remaining issues towards providing a coherent framework. We outline common lessons learned and use them as the basis for generalizations for the design of networked exertion games. We propose possible directions of further investigation, hoping to provide guidance for future work to facilitate greater awareness and exposure of exertion games and their benefits.
Piriformospora indica Root Colonization Triggers Local and Systemic Root Responses and Inhibits Secondary Colonization of Distal Roots
Lorenzo Pedrotti, Martin J. Mueller, Frank Waller
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069352
Abstract: Piriformospora indica is a basidiomycete fungus colonizing roots of a wide range of higher plants, including crop plants and the model plant Arabidopsis thaliana. Previous studies have shown that P. indica improves growth, and enhances systemic pathogen resistance in leaves of host plants. To investigate systemic effects within the root system, we established a hydroponic split-root cultivation system for Arabidopsis. Using quantitative real-time PCR, we show that initial P. indica colonization triggers a local, transient response of several defense-related transcripts, of which some were also induced in shoots and in distal, non-colonized roots of the same plant. Systemic effects on distal roots included the inhibition of secondary P. indica colonization. Faster and stronger induction of defense-related transcripts during secondary inoculation revealed that a P. indica pretreatment triggers root-wide priming of defense responses, which could cause the observed reduction of secondary colonization levels. Secondary P. indica colonization also induced defense responses in distant, already colonized parts of the root. Endophytic fungi therefore trigger a spatially specific response in directly colonized and in systemic root tissues of host plants.
Balancing torques in membrane-mediated interactions: Exact results and numerical illustrations
Martin Michael Mueller,Markus Deserno,Jemal Guven
Physics , 2007, DOI: 10.1103/PhysRevE.76.011921
Abstract: Torques on interfaces can be described by a divergence-free tensor which is fully encoded in the geometry. This tensor consists of two terms, one originating in the couple of the stress, the other capturing an intrinsic contribution due to curvature. In analogy to the description of forces in terms of a stress tensor, the torque on a particle can be expressed as a line integral along any contour surrounding the particle. Interactions between particles mediated by a fluid membrane are studied within this framework. In particular, torque balance places a strong constraint on the shape of the membrane. Symmetric two-particle configurations admit simple analytical expressions which are valid in the fully nonlinear regime; in particular, the problem may be solved exactly in the case of two membrane-bound parallel cylinders. This apparently simple system provides some flavor of the remarkably subtle nonlinear behavior associated with membrane-mediated interactions.
How to determine local elastic properties of lipid bilayer membranes from atomic-force-microscope measurements: A theoretical analysis
Davood Norouzi,Martin Michael Mueller,Markus Deserno
Physics , 2006, DOI: 10.1103/PhysRevE.74.061914
Abstract: Measurements with an atomic force microscope (AFM) offer a direct way to probe elastic properties of lipid bilayer membranes locally: provided the underlying stress-strain relation is known, material parameters such as surface tension or bending rigidity may be deduced. In a recent experiment a pore-spanning membrane was poked with an AFM tip, yielding a linear behavior of the force-indentation curves. A theoretical model for this case is presented here which describes these curves in the framework of Helfrich theory. The linear behavior of the measurements is reproduced if one neglects the influence of adhesion between tip and membrane. Including it via an adhesion balance changes the situation significantly: force-distance curves cease to be linear, hysteresis and nonzero detachment forces can show up. The characteristics of this rich scenario are discussed in detail in this article.
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