796 research outputs found
Cavity Optomechanical Magnetometer
A cavity optomechanical magnetometer is demonstrated where the magnetic field
induced expansion of a magnetostrictive material is transduced onto the
physical structure of a highly compliant optical microresonator. The resulting
motion is read out optically with ultra-high sensitivity. Detecting the
magnetostrictive deformation of Terfenol-D with a toroidal whispering gallery
mode (TWGM) resonator a peak sensitivity of 400 nT/Hz^.5 was achieved with
theoretical modelling predicting that sensitivities of up to 500 fT/Hz^.5 may
be possible. This chip-based magnetometer combines high-sensitivity and large
dynamic range with small size and room temperature operation
Expression of ECM proteins fibulin-1 and -2 in acute and chronic liver disease and in cultured rat liver cells
Fibulin-2 has previously been considered as a marker to distinguish rat liver myofibroblasts from hepatic stellate cells. The function of other fibulins in acute or chronic liver damage has not yet been investigated. The aim of this study has been to evaluate the expression of fibulin-1 and -2 in models of rat liver injury and in human liver cirrhosis. Their cellular sources have also been investigated. In normal rat liver, fibulin-1 and -2 were both mainly present in the portal field. Fibulin-1-coding transcripts were detected in total RNA of normal rat liver, whereas fibulin-2 mRNA was only detected by sensitive, real-time quantitative polymerase chain reaction. In acute liver injury, the expression of fibulin-1 was significantly increased (17.23-fold after 48 h), whereas that of fibulin-2 was not modified. The expression of both fibulin-1 and -2 was increased in experimental rat liver cirrhosis (19.16- and 26.47-fold, respectively). At the cellular level, fibulin-1 was detectable in hepatocytes, “activated” hepatic stellate cells, and liver myofibroblasts (2.71-, 122.65-, and 469.48-fold over the expression in normal rat liver), whereas fibulin-2 was restricted to liver myofibroblasts and was regulated by transforming growth factor beta-1 (TGF-β1) in 2-day-old hepatocyte cultures and in liver myofibroblasts. Thus, fibulin-1 and -2 respond differentially to single and repeated damaging noxae, and their expression is differently present in liver cells. Expression of the fibulin-2 gene is regulated by TGF-β1 in liver myofibroblasts
Detection and characterization of web vibrations by artificial vision
In this paper, we address the problem of the detection of transverse web vibrations by means of a digital camera and a laser dots pattern device. For this purpose, we briefly present some video processings which yield an accurate location of the projection of laser dots in the image. However, the main contribution of this work is in the new approach developed for estimating, on-line, transverse web vibration frequencies with a geometrical method and without contact. To do so, some techniques commonly used in the computer vision field are extended to some classes of non-rigid objects suitable to account for a part of an elastic web. Finally, we compare the estimated frequencies with those provided by a simple vibrating elastic string model, in motion
Fundamental constraints on particle tracking with optical tweezers
A general quantum limit to the sensitivity of particle position measurements
is derived following the simple principle of the Heisenberg microscope. The
value of this limit is calculated for particles in the Rayleigh and Mie
scattering regimes, and with parameters which are relevant to optical tweezers
experiments. The minimum power required to observe the zero-point motion of a
levitating bead is also calculated, with the optimal particle diameter always
smaller than the wavelength. We show that recent optical tweezers experiments
are within two orders of magnitude of quantum limited sensitivity, suggesting
that quantum optical resources may soon play an important role in high
sensitivity tracking applications
Recent advances in web longitudinal control
Stable web transport through processing machinery is critical in the web processing industry. Demands for improved performance under a wide variety of dynamic conditions and web materials are placing additional emphasis on developing new advanced control techniques. Further, technological advances in areas such as drive hardware, microprocessors, and sensors, are opening up new possibilities for implementing advanced control methods that are robust to a number of process and material variations and result in superior performance over existing industrial control methods.Mathematical models of fundamentals elements in a web process line are presented. A systematic procedure for computing the equilibrium inputs as well as reference velocities of all rollers based on the master speed reference is given. Recently developed robust control methods for web longitudinal control are described. Implementation of the controllers on two experimental platforms is given, and a sample of the experimental results is presented. Finally, some potential new directions and future research topics are discussed.Mechanical and Aerospace Engineerin
Sensitivity of cavity optomechanical field sensors
This article presents a technique for modeling cavity optomechanical field sensors. A magnetic or electric field induces a spatially varying strain across the sensor. The effect of this strain is accounted for by separating the mechanical motion of the sensor into eigenmodes, each modeled by a simple harmonic oscillator. The force induced on each oscillator can then be determined from an overlap integral between strain and the corresponding eigenmode, with the optomechanical coupling strength determining the ultimate resolution with which this force can be detected
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