41 research outputs found
Denkwürdigkeiten des Philosophen und Arztes Johann Benjamin Erhard
No full textherausgeben von K. A. Varnhagen von EnseErmittelter Name: Karl August Varnhagen von EnseExlibrisetikette: "Aus der Bibliothek von Oberstdivisionär Eugen Bircher Aarau der Bibliothek der Eidgenössischen Technischen Hochschule geschenkt" 002129036_0001 Exemplar der ETH-BIBFrühere Signatur: "Bircher 1805" 990019806050205503_0003 Exemplar der ETH-BIBExlibrisstempel: "Antiquariat-Buchhandlung Oskar Kahl, Dresden-A., kl. Kirchgasse 3" 990019806050205503_0002 Exemplar der ETH-BIBExlibrisetikette: "Lese-Verein" 990019806050205503_0001 Exemplar der ETH-BI
Fluid characterization by resonant nanomechanical sensing
No full textMicrofluidic technologies allow handling and characterizing liquid samples on the micro- to picoliter scale. Thereby, the viscosity and mass density are key properties of such samples, because they characterize their flow behavior. The viscosity of a liquid indicates its resistance to flow, whereas the density quantifies the mass per volume. Molecular transformations, such as chemical polymerization, protein folding and aggregation, or nucleic acid hybridization, influence both properties. Therefore, measuring them is fundamental for basic research, quality control, and process monitoring. Since many, especially biological, samples are only available in small quantities and/or expensive, reducing sample consumption is essential. Furthermore, the acquisition time of viscosity measurements nowadays is on the order of minutes, limiting the characterization of large numbers of samples. Hence, increasing the time resolution and the throughput is another significant requirement.
It was early noticed that the dynamics of nanomechanical resonators are strongly influenced by the surrounding fluid. This effect can be utilized to measure the fluid properties, specifically the viscosity and mass density. In this thesis, resonant nanomechanical cantilevers were, therefore, employed with focus on the application of higher modes of vibration.
First, a suitable method to excite and detect the strongly damped cantilever resonances encountered in liquid was realized: Photothermal excitation uses an intensity-modulated laser to induce cantilever vibration. Its direct and local energy transfer avoids distortions arising in prevalent excitation methods, such as piezo-acoustic excitation, and results in spurious-free resonance spectra. To detect the nanometer vibrations of the cantilevers, a second laser was used in an optical beam deflection configuration. Such optical excitation/detection method is accurate and robust, however, it is only suitable for transparent liquids. Technical details about the developed setup are provided in the appendix of this thesis. Due to the small dimensions of the microfluidic channel containing the cantilever sensors, the influence of proximate surfaces was investigated. Placing a vibrating cantilever below a critical distance to a surface induces squeeze-film damping. The magnitude and range of this undesirable effect on higher mode vibrations was characterized and incorporated in the fluid channel design. The above findings are generally applicable to atomic force microscopy and nanomechanical sensing in liquid.
Next, the ability of the sensor to measure viscosity and mass density of liquids was assessed. Dynamic properties of the cantilever resonator were derived from resonance spectra and converted into the surrounding liquid properties, using adapted hydrodynamic models. Multiple modes of vibration covered a broad frequency range in the order of kHz to MHz. A stringent temperature control was implemented, due to the high temperature dependency of the measured parameters. To investigate time-resolved processes, free-radical polymerization reactions were tracked and characterized. The shear-thinning behavior of the polymer solutions, i.e., the non-Newtonian effect of decreasing viscosity with increasing frequency, was resolved by the instrument. The time to characterize a 5 µL sample was on the order of 1 min.
Finally, the setup was optimized for automated high-throughput screening of microliter sample droplets. The droplets were generated by an automated sampler and separated by fluorinated oil. To achieve the required time resolution, a higher vibrational mode was tracked using two phase-locked loop demodulators. This allowed to derive the viscosity and mass density of the liquid surrounding the resonator with a temporal resolution of about 1 ms. The instrument was able to detect ~1 µL droplets at a rate on the order of 1 s per droplet.
The developed viscosity and mass density sensor opens several possibilities. We recently initiated the study of stimulus-responsive polymers for glucose sensing and the unfolding behavior of proteins. This, by solely measuring changes in viscosity after introducing the analyte or inducing denaturation. Future work could involve monitoring of RNA hybridization and protein aggregation into fibrils
Hertz-inniger Andachts-Spiegel, oder Vollständiges und kurtzgefastes Gebet-Buch : Worinnen nebst denen sonderbaren Morgen- Abend- Buß- Beicht- Communion- und andern, so wohl täglichen allgemeinen, als auch sonderbaren Bitten, Gebeten, Fürbitten, Dan
No full textIdentity of author is unclear. Bircher claims it is Paul Kaim; Holzmann/Bohatta gives Nikolaus Häublein.; Signatures: A?-I? (H? mislabeled.; Page numbers 15-16 lacking. Signature complete: leaves A3-A6 mislabeled as A2-A5. Catchword correct.; Not in VD 17.; Label of the Library of the Congregation of U.B. of the Borough of Bethlehem and its vicinity. No 1419.; This title is bound with ""Helleleuchtender Hertzens-Spiegel..."" [CongLib 1419 [1]].; Bircher, M. Barock, 1600-1720,; Holzmann & Bohatta. Deutsches Anonymenlexikon
Low-Cost 2D Index and Straightness Measurement System Based on a CMOS Image Sensor
No full textAccurate traceable measurement systems often use laser interferometers for position measurements in one or more dimensions. Since interferometers provide only incremental information, they are often combined with index sensors to provide a stable reference starting point. Straightness measurements are important for machine axis correction and for systems having several degrees of freedom. In this paper, we investigate the accuracy of an optical two-dimensional (2D) index sensor, which can also be used in a straightness measurement system, based on a fiber-coupled, collimated laser beam pointing onto an image sensor. Additionally, the sensor can directly determine a 2D position over a range of a few millimeters. The device is based on a simple and low-cost complementary metal–oxide–semiconductor (CMOS) image sensor chip and provides sub-micrometer accuracy. The system is an interesting alternative to standard techniques and can even be implemented on machines for real-time corrections. This paper presents the developed sensor properties for various applications and introduces a novel error separation method for straightness measurements
Influence of squeeze-film damping on higher-mode microcantilever vibrations in liquid
No full textThe functionality of atomic force microscopy (AFM) and nanomechanical sensing can be enhanced using higher-mode microcantilever vibrations. Both methods require a resonating microcantilever to be placed close to a surface, either a sample or the boundary of a microfluidic channel. Below a certain cantilever-surface separation, the confined fluid induces squeeze-film damping. Since damping changes the dynamic properties of the cantilever and decreases its sensitivity, it should be considered and minimized. Although squeeze-film damping in gases is comprehensively described, little experimental data is available in liquids, especially for higher-mode vibrations. We have measured the flexural higher-mode response of photothermally driven microcantilevers vibrating in water, close to a parallel surface with gaps ranging from ~200 μm to ~1 μm. A modified model based on harmonic oscillator theory was used to determine the modal eigenfrequencies and quality factors, which can be converted into co-moving fluid mass and dissipation coefficients. The range of squeeze-film damping between the cantilever and surface decreased for eigenfrequencies (inertial forces) and increased for quality factors (dissipative forces) with higher mode number. The results can be employed to improve the quantitative analysis of AFM measurements, design miniaturized sensor fluid cells, or benchmark theoretical models
Automated high-throughput viscosity and density sensor using nanomechanical resonators
No full textAbstractMost methods used to determine the viscosity and mass density of liquids have two major drawbacks: relatively high sample consumption (∼milliliters) and long measurement time (∼minutes). Resonant nanomechanical cantilevers promise to overcome these limitations. Although sample consumption has already been significantly reduced, the time resolution was rarely addressed to date. We present a method to decrease the time and user interaction required for such measurements. It features (i) a droplet-generating automatic sampler using fluorinated oil to separate microliter sample plugs, (ii) a PDMS-based microfluidic measurement cell containing the resonant microcantilever sensors driven by photothermal excitation, (iii) dual phase-locked loop frequency tracking of a higher-mode resonance to achieve millisecond time resolution, and (iv) signal processing to extract the resonance parameters, namely the eigenfrequency and quality factor. The principle was validated by screening series of 3μL droplets of glycerol solutions separated by fluorinated oil at a rate of ∼6s per sample. An analytical hydrodynamic model (Van Eysden and Sader, 2007 [6]) and a reduced order model (Heinisch et al., 2014 [16]) were employed to calculate the viscosity and mass density of the sample liquids in a viscosity range of 1–10.5mPas and a density range of 998–1154kgm−3
Regulation of Trio GEF1 Activity by the Spectrin Repeats and Cellular Factors
No full textThe Trio family of proteins consists of Trio, Kalirin, UNC-73 (in Caenorhabditis elegans) and dTrio (in Drosophila). Trio proteins are key regulators of cell morphogenesis and migration, tissue organization, and secretion and protein trafficking in many biological contexts. Recent discoveries have linked Trio and Kalirin to human disease, including neurological disorders and cancer. The genes for Trio family proteins encode a series of large multidomain proteins with up to three catalytic activities and multiple scaffolding and protein-protein interaction domains. As such, Trio family proteins engage a wide array of cell surface receptors, substrates, and interaction partners to coordinate changes in cytoskeletal regulatory and protein trafficking pathways. In Chapter 1, I provide a comprehensive review of the specific mechanisms by which Trio family proteins carry out their functions in cells, highlight the biological and cellular contexts in which they occur, and relate how alterations in these functions contribute to human disease. This sets up the context for a major goal of my thesis, which was to elucidate a regulatory mechanism of Trio catalytic activity and understand how disease associated mutations disrupt this regulation. In Chapter 2, I describe my co-first author work, which uncovered a mode of Trio regulation. The Trio spectrin repeats (SRs) are adjacent to the Trio GEF1 domain and disease-associated mutations to the SRs have been shown to impact Trio GEF1 activity. I provide evidence that the Trio SRs autoinhibit Trio GEF1 activity via intramolecular interactions, and this is relieved by disease-associated mutations. In Chapter 3, I discuss unpublished work to understand how Trio is regulated in a cellular context. I cover my work to generate a Trio knockout fibroblast cell line and discover activators of the autoinhibited Trio GEF1 activity. This preliminary work is supported by Chapter 4, in which I describe the most pressing future experiments and approaches I recommend to follow up my thesis work. Together, the work described in this thesis provides insight into a novel mechanism of Trio regulation and sets up a framework for many exciting future discoveries
Characterising the Positioning System of a Dimensional Computed Tomograph (CT)
No full textComputed tomography (CT) is increasingly used for dimensional characterisation of workpieces. Therefore, the Federal Institute of Metrology METAS is developing and building a unique metrology CT system to measure workpieces of millimetre dimensions with sub-micrometre resolution, and to study CT metrology and traceability in general. Here, an overview of the CT system is presented and the requirements related to the positioning system and its characterisation are discussed in detail. The results indicate that further in situ measurement systems are required to correct high-resolution CT scans for geometrical errors.This article is based on a presentation at the conference "MacroScale 2017 - Recent developments in traceable dimensional measurements", VTT MIKES Espoo, (Finnland), 17th-19th October 2017
Les systèmes d'information et la vie privée du salarié : analyse en droit européen, en droit suisse et en droit français
No full textAs a result of information and communication technologies, ties of a legal, social economic and organisational nature between employee and employer have changed. Use of technology impacts several areas and dimensions of the working arrangement that are inextricably linked to the employee’s personal status. Using Article 8 EDHR as the leitmotiv and main source of analysis, this thesis reaffirms that employment law and human rights law are intertwined, and that Article 8 EDHR can be applied to relations between worker and employer. Using a comparative approach, the author analyses employees’ rights to privacy under European, French and Swiss law — highlighting their differences and shortcoming in relation to each other. Part one lays the foundation of employees’ rights to privacy with regard to family life, home life, correspondence and data protection. The delicate balance between the interests of the company in safeguarding its security and those of the worker in protecting his or her private life are analysed. Part two deals with the way in which privacy protection can be implemented, looking at the drafting of standards, types of regulation and the application made of the latter by national oversight bodies and by agents inside and outside the company. The research demonstrates that, on the basis of comparative analysis, improved protection of basic rights to employee privacy can legitimately be put in place through a company’s bylaws, preferably through discussions and negotiations with social partners. The goal is to shield employees’ privacy, not only in theory but most importantly in practice.Par les technologies de l'information et de la communication, les liens juridiques, sociaux, économiques et organisationnels entre le salarié et l'employeur se sont modifiés. L'usage des technologies a des effets sur de nombreux aspects oudimensions du travail qui sont intimement liés à la personne même du salarié. Avec l'article 8 CEDH comme fil conducteur et source principale des réflexions, la thèse réaffirme que le droit du travail et celui des droits de l'homme sont intimementliés et que l'article 8 CEDH s'applique aux relations entre travailleur et employeur. A l'aide d'une approche comparative, l’auteur analyse le droit à la vie privée du salarié en droit européen, en droit français et en droit suisse en faisant apparaître lesdifférences et les lacunes de l’un ou de l’autre droit. La première partie pose les bases du droit à la vie privée du salarié (vie familiale, domicile, correspondance, protection des données). Le difficile équilibre entre les intérêts de l'entreprise à sauvegarder sa sécurité et celui du travailleur à préserver son intimité fait l'objet de l'analyse. La deuxième partie traite de la mise en oeuvre de la protection de la vie privée du salarié en passant par l'élaboration des normes, les types de régulation etl'application qui en est faite par les autorités de surveillance nationales et par les autres acteurs internes ou externes à l'entreprise. La thèse démontre, sur la base d'une analyse comparée, qu' une meilleure protection du droit fondamental à la vie privée du salarié peut être valablement mise en oeuvre par le biais d'un règlement interne à l'entreprise, si possible discuté et négocié entre les partenaires sociaux. L'objectif est de protéger le droit à la vie privée de l'employé, non seulement en théorie, mais surtout en pratique
