302 research outputs found
Reizdarmsyndrom
Zusammenfassung: Das Reizdarmsyndrom (engl. "irritable bowel syndrome", IBS) ist ein gastrointestinales Krankheitsbild, welches durch chronische Bauchschmerzen oder Unwohlsein und Stuhlunregelmäßigkeiten ohne den Nachweis einer organischen Ursache charakterisiert ist. Erst vor kurzem wurden die Rom-Kriterien, eine Klassifikation der funktionellen gastrointestinalen Erkrankungen, auch für das Kindes- und Jugendalter angepasst. Die Prävalenz des IBS liegt ungefähr zwischen 5 und 15%. Nur etwa 10-30% der Betroffenen beanspruchen ärztliche Hilfe. Beim Fehlen von Alarmsymptomen und chronischer Diarrhö ist die Durchführung einer Basisdiagnostik ausreichend. Ätiologie und Pathogenese sind unklar. Eine Motilitätsstörung und eine viszerale Hypersensitivität spielen möglicherweise neben anderen Faktoren eine Rolle. Die Therapie ist symptomatisch und muss dem einzelnen Patienten angepasst erfolge
Influence of electromagnetic interferences on the gravimetric sensitivity of surface acoustic waveguides
Surface acoustic waveguides are increasing in interest for (bio)chemical
detection. The surface mass modification leads to measurable changes in the
propagation properties of the waveguide. Among a wide variety of waveguides,
Love mode has been investigated because of its high gravimetric sensitivity.
The acoustic signal launched and detected in the waveguide by electrical
transducers is accompanied by an electromagnetic wave; the interaction of the
two signals, easily enhanced by the open structure of the sensor, creates
interference patterns in the transfer function of the sensor. The influence of
these interferences on the gravimetric sensitivity is presented, whereby the
structure of the entire sensor is modelled. We show that electromagnetic
interferences generate an error in the experimental value of the sensitivity.
This error is different for the open and the closed loop configurations of the
sensor. The theoretical approach is completed by the experimentation of an
actual Love mode sensor operated under liquid in open loop configuration. The
experiment indicates that the interaction depends on the frequency and the mass
modifications.Comment: 28 pages, 8 figure
High-overtone Bulk-Acoustic Resonator gravimetric sensitivity: towards wideband acoustic spectroscopy
In the context of direct detection sensors with compact dimensions, we
investigate the gravimetric sensitivity of High-overtone Bulk Acoustic
Resonators, through modeling of their acoustic characteristics and experiment.
The high frequency characterizing such devices is expected to induce a
significant effect when the acoustic field boundary conditions are modified by
a thin adlayer. Furthermore, the multimode spectral characteristics is
considered for wideband acoustic spectroscopy of the adlayer, once the
gravimetric sensitivity dependence of the various overtones is established.
Finally, means of improving the gravimetric sensitivity by confining the
acoustic field in a low acoustic-impedance layer is theoretically established.Comment: 9 pages, 10 figures in J. Appl. Phys. 201
INTERACTIONS AND PRECIPITATIONS IN DILUTE TERNARY Fe Sb M ALLOYS (M = Ti, V, Cr, Mn, Co, AND Ni)
No abstract availabl
Simultaneous surface acoustic wave and surface plasmon resonance measurements: electrodeposition and biological interactions monitoring
We present results from an instrument combining surface acoustic wave (SAW)
propagation and surface plasmon resonance (SPR) measurements. The objective is
to use two independent methods, the former based on adsorbed mass change
measurements and the latter on surface dielectric properties variations, to
identify physical properties of protein layers, and more specifically their
water content. We display mass sensitivity calibration curves using
electrodeposition of copper leading to a sensitivity in liquid of 150
for the Love mode device used here, and the application to monitoring
biological processes. The extraction of protein layer thickness and protein to
water content ratio is also presented for S-layer proteins under investigation.
We obtain respectively 4.70.7 nm and 7515%.Comment: 13 pages, 4 figure
Magnetic excitations in the metallic single-layer Ruthenates Ca(2-x)Sr(x)RuO(4) studied by inelastic neutron scattering
By inelastic neutron scattering, we have analyzed the magnetic correlations
in the paramagnetic metallic region of the series Ca(2-x)Sr(x)RuO(4),
0.2<=x<=0.62. We find different contributions that correspond to 2D
ferromagnetic fluctuations and to fluctuations at incommensurate wave vectors
(0.11,0,0), (0.26,0,0) and (0.3,0.3,0). These components constitute the
measured response as function of the Sr-concentration x, of the magnetic field
and of the temperature. A generic model is applicable to metallic
Ca(2-x)Sr(x)RuO(4) close to the Mott transition, in spite of their strongly
varying physical properties. The amplitude, characteristic energy and width of
the incommensurate components vary only little as function of x, but the
ferromagnetic component depends sensitively on concentration, temperature and
magnetic field. While ferromagnetic fluctuations are very strong in
Ca1.38Sr0.62RuO4 with a low characteristic energy of 0.2 meV at T=1.5 K, they
are strongly suppressed in Ca1.8Sr0.2RuO4, but reappear upon the application of
a magnetic field and form a magnon mode above the metamagnetic transition. The
inelastic neutron scattering results document how the competition between
ferromagnetic and incommensurate antiferromagnetic instabilities governs the
physics of this system
Optimal estimation for Large-Eddy Simulation of turbulence and application to the analysis of subgrid models
The tools of optimal estimation are applied to the study of subgrid models
for Large-Eddy Simulation of turbulence. The concept of optimal estimator is
introduced and its properties are analyzed in the context of applications to a
priori tests of subgrid models. Attention is focused on the Cook and Riley
model in the case of a scalar field in isotropic turbulence. Using DNS data,
the relevance of the beta assumption is estimated by computing (i) generalized
optimal estimators and (ii) the error brought by this assumption alone. Optimal
estimators are computed for the subgrid variance using various sets of
variables and various techniques (histograms and neural networks). It is shown
that optimal estimators allow a thorough exploration of models. Neural networks
are proved to be relevant and very efficient in this framework, and further
usages are suggested
In Situ Evaluation of Density, Viscosity and Thickness of Adsorbed Soft Layers by Combined Surface Acoustic Wave and Surface Plasmon Resonance
We show the theoretical and experimental combination of acoustic and optical
methods for the in situ quantitative evaluation of the density, the viscosity
and the thickness of soft layers adsorbed on chemically tailored metal
surfaces. For the highest sensitivity and an operation in liquids, a Love mode
surface acoustic wave (SAW) sensor with a hydrophobized gold coated sensing
area is the acoustic method, while surface plasmon resonance (SPR) on the same
gold surface as the optical method is monitored simultaneously in a single
set-up for the real-time and label-free measurement of the parameters of
adsorbed soft layers, which means for layers with a predominant viscous
behavior. A general mathematical modeling in equivalent viscoelastic
transmission lines is presented to determine the correlation between
experimental SAW signal shifts and the waveguide structure including the
presence of the adsorbed layer and the supporting liquid from which it
segregates. A methodology is presented to identify from SAW and SPR simulations
the parameters representatives of the soft layer. During the absorption of a
soft layer, thickness or viscosity changes are observed in the experimental
ratio of the SAW signal attenuation to the SAW signal phase and are correlated
with the theoretical model. As application example, the simulation method is
applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose
conformation is sensitive to temperature, under a cycling variation of
temperature between 20 and 40 oC. Under the assumption of the bulk density and
the bulk refractive index of PNIPAAm, thickness and viscosity of the film are
obtained from simulations; the viscosity is correlated to the solvent content
of the physisorbed layer.Comment: 61 pages previous submission replaced by this manuscript including
corrections following comments of Anal. Chem. reviewers: new transmission
line model and assessing viscosity/thickness results. Missing figure of
NIPAAM structure due to LaTeX compilation error
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