87 research outputs found
Development of Multifunctional Overhauser-enhanced Magnetic Rresonance Imaging for Concurrent in Vivo Mapping of Tumor Interstitial Oxygenation, Acidosis and Inorganic Phosphate Concentration
Tumor oxygenation (pO2), acidosis (pH) and interstitial inorganic phosphate concentration (Pi) are important parameters of the malignant behavior of cancer. A noninvasive procedure that enables visualization of these parameters may provide unique information about mechanisms of tumor pathophysiology and provide clues to new treatment targets. In this research, we present a multiparametric imaging method allowing for concurrent mapping of pH, spin probe concentration, pO2, and Pi using a single contrast agent and Overhauser-enhanced magnetic resonance imaging technique. The developed approach was applied to concurrent multifunctional imaging in phantom samples and in vivo in a mouse model of breast cancer. Tumor tissues showed higher heterogeneity of the distributions of the parameters compared with normal mammary gland and demonstrated the areas of significant acidosis, hypoxia, and elevated Pi content
Scaling and Crossover to Tricriticality in Polymer Solutions
We propose a scaling description of phase separation of polymer solutions.
The scaling incorporates three universal limiting regimes: the Ising limit
asymptotically close to the critical point of phase separation, the "ideal-gas"
limit for the pure-solvent phase, and the tricritical limit for the
polymer-rich phase asymptotically close to the theta point. We have also
developed a phenomenological crossover theory based on the
near-tricritical-point Landau expansion renormalized by fluctuations. This
theory validates the proposed scaled representation of experimental data and
crossover to tricriticality.Comment: 4 pages, 3 figure
Dislocation loops in overheated free-standing smectic films
Static and dynamic phenomena in overheated free-standing smectic-A films are
studied using a generalization of de Gennes' theory for a confined presmectic
liquid. A static application is to determine the profile of the film meniscus
and the meniscus contact angle, the results being compared with those of a
recent study employing de Gennes' original theory. The dynamical generalization
of the theory is based on on a time-dependent Ginzburg-Landau approach. This is
used to compare two modes for layer-thinning transitions in overheated films,
namely "uniform thinning" vs. nucleation of dislocation loops. Properties such
as the line tension and velocity of a moving dislocation line are evaluated
self-consistently by the theory.Comment: 16 pages, 8 figure
Multi-agent Solution for Adaptive Data Analysis in Sensor Networks at the Intelligent Hospital Ward
Oxygen-induced leakage of spin polarization in Overhauser- enhanced magnetic resonance imaging: Application for oximetry in tumors
Overhauser-enhanced Magnetic Resonance Imaging (OMRI) is a double resonance technique applied for oxygen imaging in aqueous samples and biological tissues. In this report, we present an improved OMRI approach of oxygen measurement using the single line “Finland” trityl spin probe. Compared to a traditional approach, we introduced an additional mechanism of leakage of spin polarization due to an interaction of a spin system with oxygen. The experimental comparison of the new approach with an oxygen-dependent leakage factor to a traditional approach performed in phantom samples in vitro, and mouse tumor model in vivo, shows improved accuracy of determination of oxygen and contrast agent concentrations
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