646 research outputs found
Computational simulation of the mechanobiological regulation of bone remodeling by means of a coupled systems biology-micromechanical approach
No full textBone remodeling involves the coordinated removal of bone by osteoclasts and addition of bone by osteoblasts, a process that is modulated by the prevailing mechanical environment. Here we present a new computational model of bone remodeling, based on coupling a bone cell population model with micromechanical homogenization of bone stiffness. As for mechanoregulation, bone remodeling is controlled proportionally to the microscopic strain energy density, on the observation scale where the sensing of the mechanical loading actually takes place, estimated by means of continuum micromechanics-based strain concentration. This new approach allows us to address how biochemical changes influence bone remodeling and thus affect the composition and mechanical properties of bone, and what mechanisms are responsible for mechanoregulation of bone remodeling. Numerical studies highlight the capabilities of the model: we demonstrate that computationally simulated changes of the bone constituent volume fractions are in qualitative agreement with experimental observations for disuse syndromes
Single Cell Analytics for NanoBiology
No full textAnselmetti D, Griemla N, Hellmich W, et al. Single Cell Analytics for NanoBiology. NanoBiotechnology. 2005;1(3):267-270
Single Cell Manipulation, Analytics and Label-free Protein Detection in Microfluidic Devices for Systems NanoBiology
No full textHellmich W, Pelargus C, Leffhalm K, Ros A, Anselmetti D. Single Cell Manipulation, Analytics and Label-free Protein Detection in Microfluidic Devices for Systems NanoBiology. In: Lion N, Roussier JS, Girault H, eds. Microfluidic Applications in Biology: From Technologies to Systems Biology. Weinheim: Wiley-VCH; 2006: 11
Role of biotechnology in sustainable agriculture
No full textA basic concept of sustainable agriculture includes using resources in a way that does not deplete or permanently damage systems used for plant and animal production. In early history, humans survived as hunter–gatherers and perhaps less than 1% of biomass could be used as food (Diamond, 1997). As a result, most resources in the environment were not likely to be used directly by humans. The limited availability of food also restricted population growth, helping to make the hunter–gatherer way of life sustainable. In contrast, domestication of crops and animals for food has greatly increased edible biomass, leading to dramatic population growth and the possibility that production of adequate food will lead to longterm damage to agricultural systems.This chapter is published as Prasifka, J. R., Hellmich, R. L. & Weiss, M. J. Role of biotechnology in sustainable agriculture. In Integrated Pest Management, edited by E. B. Radcliffe, W. D. Hutchison & R. E. Cancelado. Cambridge University Press. 2009.</p
Dekohärenz in unendlichen Quantensystemen
No full textHellmich M. Decoherence in infinite quantum systems. Bielefeld (Germany): Bielefeld University; 2009.Die Quantenmechanik gilt heute als unsere grundlegendste physikalische Theorie. Als solche beschränkt sie sich nicht nur auf ihre ursprünglichen Anwendungsbereiche wie die Atomphysik, Elementarteilchenphysik und die Quantenfeldtheorie, sondern ihr Gegenstandsbereich sollte auch makroskopische Systeme einschließen, die den Gesetzen der klassischen Physik gehorchen. Hier stößt man jedoch auf ein fundamentales Problem: Wendet man die Gesetze der Quantenmechanik direkt auf die Objekte unserer Alltagswelt an, so gelangt man zu Widersprüchen. Der wahrscheinlich berühmteste ist die Schrödinger-Katze, die sich in einem nichtklassischen Zustand befindet, der eine kohärente Überlagerung des Zustandes "tot" und "lebendig" der Katze darstellt.
Die Theorie der Dekohärenz bietet eine Lösung dieser Probleme. Sie geht davon aus, dass die Quantenmechanik universell gültig ist, man jedoch zu berücksichtigen hat, dass makroskopische Systeme gewöhnlich stark mit ihrer Umgebung in Wechselwirkung stehen. Durch diese Wechselwirkung wird die Zeitentwicklung des betrachteten Systems irreversibel, und diese Irreversibilität ist in der Lage, klassische Effekte dynamisch zu erzeugen. Genauer gesprochen bewirkt die Wechselwirkung eine starke Verschränkung zwischen System und Umgebung, welche Phasenfaktoren zwischen Vektoren bestimmter Unterräume des Hilbertraumes des Systems unbeobachtbar macht und somit das Superpositionsprinzip einschränkt, welches nichtklassische Zustände wie im Beispiel der Schrödinger-Katze erlaubt.
Bisher konzentrierten sich die meisten Arbeiten zur Dekohärenz auf Systeme mit endlichdimensionalem Hilbertraum oder auf Systeme mit endlich vielen Freiheitsgraden. Die Theorie der Dekohärenz und irreversibler Zeitentwicklungen für Systeme mit unendlich vielen Freiheitsgraden ist weit weniger fortgeschritten. Es ist das Ziel der vorliegenden Arbeit, einige allgemeine Resultate über Dekohärenz in Systemen mit Markoffscher Zeitentwicklung beizusteuern, die hinreichend allgemein sind, um auch für unendliche Systeme ihre Gültigkeit zu behalten. Ein zweiter Aspekt ist die mathematisch rigorose Konstruktion von irreversiblen Zeitentwicklungen auf Darstellungen der Algebra der kanonischen Vertauschungsrelationen (CCR-Algebra).Today quantum mechanics is considered as the most fundamental physical theory available. As such it is not limited to its traditional areas like atomic and elementary particle physics and quantum field theory, but its scope should also contain macroscopic systems, obeying the laws of classical physics. Here a fundamental problem arises: when the laws of quantum mechanics are directly applied to the objects of our everyday field of experience, contradictions arise. Probably the most famous example is the Schrödinger cat, which exists in a nonclassical state which is a superposition of the "dead" and "alive" state of the cat.
The program of environmental decoherence provides an answer to these problems. It contends that quantum mechanics is universally valid but that one has to take into account that macroscopic systems are usually strongly interacting with their environment. This interaction causes the time evolution of the system to become irreversible, and irreversibility is able to dynamically generate classical properties. Specifically, the interaction between system and environment leads to a strong entanglement between them which effectively renders phase relations between vectors from certain subspaces of the system's Hilbert space unobservable, thus limiting the superposition principle which is responsible for nonclassical behavior like in the Schrödinger cat example.
Up to now most studies on decoherence have been concentrating on systems describable by a finite-dimensional Hilbert space or standard quantum mechanics with finitely many degrees of freedom. The theory of irreversible dynamics and decoherence of systems with infinitely many degrees of freedom in contrast is far less advanced. It is the objective of this work to provide some general results about decoherence in systems with Markovian time evolution which are sufficiently general to cover also infinite systems. A second aspect is to construct irreversible dynamics on representations of the algebra of canonical commutation relations (CCR algebra) in a mathematically rigorous way and to study their properties
Acute coronary syndrome in Takayasu arteritis without elevation of acute phase parameters
No full textImproved native UV laser induced fluorescence detection for single cell analysis in poly(dimethylsiloxane) microfluidic devices
No full textHellmich W, Greif D, Pelargus C, Anselmetti D, Ros A. Improved native UV laser induced fluorescence detection for single cell analysis in poly(dimethylsiloxane) microfluidic devices. In: Journal of Chromatography A. JOURNAL OF CHROMATOGRAPHY A. Vol 1130. ELSEVIER SCIENCE BV; 2006: 195-200.Single cell analytics is a key method in the framework of proteom research allowing analyses, which are not subjected to ensemble-averaging, cell-cycle or heterogeneous cell-population effects. Our previous studies on single cell analysis in poly(dimethylsiloxane) microfluidic devices with native label-free laser induced fluorescence detection [W. Hellmich, C. Pelargus, K. Leffhalm, A. Ros, D. Anselmetti, Electrophoresis 26 (2005) 3689] were extended in order to improve separation efficiency and detection sensitivity. Here, we particularly focus on the influence of poly(oxyethylene) based coatings on the separation performance. In addition, the influence on background fluorescence is studied by the variation of the incident laser power as well as the adaptation of the confocal volume to the microfluidic channel dimensions. Last but not least, the use of carbon black particles further enhanced the detection limit to 25 nM, thereby reaching the relevant concentration ranges necessary for the label-free detection of low abundant proteins in single cells. On the basis of these results, we demonstrate the first electropherogram from an individual Spodoptera frugiperda (Sf9) cell with native label-free UV-LIF detection in a microfluidic chip. (c) 2006 Elsevier B.V. All rights reserved
Towards single cell fingerprinting in microfluidic device format : single cell manipulation, protein separation and detection
No full textHellmich W, Leffhalm K, Sischka A, et al. Towards single cell fingerprinting in microfluidic device format : single cell manipulation, protein separation and detection. In: Jensen KF, ed. Micro total analysis systems 2005. Proceedings of µTAS 2005. Conference Proceedings on Miniaturized Systems for Chemistry and Life Sciences (µTAS). Vol 1. Boston: The Chemical and Biological Microsystems Society (CBMS); 2005: 406-408
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