A new instrument for simultaneous microbeam small-and wide-angle X-ray scattering and X-ray fluorescence (SAXS/WAXS/XRF) is presented. The instrument is installed at the microfocus beamline at BESSY II and provides a beam of 10 mm size with a flux of about 10 9 photons s
À1. A SAXS resolution up to 500 Å d-spacing and a range of scattering vectors of almost three orders of magnitude are reached by using a large-area high-resolution CCD-based detector for simultaneous SAXS/WAXS. The instrument is particularly suited for scanning SAXS/WAXS/XRF experiments on hierarchically structured biological tissues. The necessary infrastructure, such as a cryo-stream facility and an on-site preparation laboratory for biological specimens, are available.
The phase properties of DPPG (dipalmitoyl-phosphatidylglycerol, sodium salt) monolayers are investigated
at different temperatures 25 °C ≤ T ≤ 34 °C where the surface pressure−area (Π−A) isotherms have large
two-phase coexistence regions. The studies are based on the thermodynamic and textural characterization of
the monolayers. The main phase transitions obtained from the Π−A isotherms are in complete agreement
with the Brewster angle microscopy results. In equilibrium, compact domains are formed which are never
really circular. The domains differ from each other in the azimuthal tilt, but they have no inner texture. Over
the entire region of the gaseous to the condensed state, the experimental Π−A isotherms are well described
by an equation of state recently derived on the basis of the generalized Volmer's equation and the quasi-chemical equilibrium model of 2D aggregation. The possible dissociation effect on the monolayer properties
of the ionic DPPG can be largely ignored, as clarified by extending the theoretical approach under consideration
of the dissociation degree of the monolayer substance. The standard thermodynamic characteristics of the 2D
aggregation are calculated for different temperatures. The analysis of these results shows that, unlike the
micelle formation, within the Langmuir monolayer the aggregation of the amphiphilic molecules to condensed
phase results only in an entropy decrease of the system due to the ordering of the amphiphilic molecules.
For the systematic development of feedback flow controllers, a numerical model that captures the dynamic behaviour of the flow field to be controlled is required. This poses a particular challenge for flow fields where the dynamic behaviour is nonlinear, and the governing equations cannot easily be solved in closed form. This has led to many versions of low-dimensional modelling techniques, which we extend in this work to represent better the impact of actuation on the flow. For the benchmark problem of a circular cylinder wake in the laminar regime, we introduce a novel extension to the proper orthogonal decomposition (POD) procedure that facilitates mode construction from transient data sets. We demonstrate the performance of this new decomposition by applying it to a data set from the development of the limit cycle oscillation of a circular cylinder wake simulation as well as an ensemble of transient forced simulation results. The modes obtained from this decomposition, which we refer to as the double POD (DPOD) method, correctly track the changes of the spatial modes both during the evolution of the limit cycle and when forcing is applied by transverse translation of the cylinder. The mode amplitudes, which are obtained by projecting the original data sets onto the truncated DPOD modes, can be used to construct a dynamic mathematical model of the wake that accurately predicts the wake flow dynamics within the lock-in region at low forcing amplitudes. This low-dimensional model, derived using nonlinear artificial neural network based system identification methods, is robust and accurate and can be used to simulate the dynamic behaviour of the wake flow. We demonstrate this ability not just for unforced and open-loop forced data, but also for a feedback-controlled simulation that leads to a 90% reduction in lift fluctuations. This indicates the possibility of constructing accurate dynamic low-dimensional models for feedback control by using unforced and transient forced data only.
An intraoperative beta probe was designed, built, and tested for detection of radio-labeled malignant tissues that has the advantage of being selectively sensitive to beta while insensitive to gamma radiation. Since beta radiation (electrons or positrons) has a short range in tissue, this probe is ideal for detecting tracers in tumors at the surface of the surgical field. This probe contains a plastic scintillation detector sensitive to beta rays and to a lesser degree some background gamma rays. A second detector counts spurious gamma rays and allows for their subtraction from the activity measured by the first detector. Sensitivity of the dual probe for I-131 and F-18 was measured to be 108 counts/s/kBq (4000 counts/s/microCi). The dual-detector probe faithfully measured the 10:1 "tumor" to background ratio of radioactivity concentrations in a simulated environment of a tumor in the presence of intense background 511 keV photons. In another phantom experiment, simulating abdominal tumor deposits with various realistic I-131 radioactive concentrations, the probe was able to accurately identify tumors of approximately 50 mg with a tumor/normal radioactivity concentration of 3/1 in 10 s.
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