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Luisa Ciobanu

Publications and source records attributed to Luisa Ciobanu.

6 recordsLinked to original sources
PubMed2006

Multiple echo NMR velocimetry: fast and localized measurements of steady and pulsatile flows in small channels.

The understanding of fluid transport in miniaturized flow devices is an important component in the design of flow cells, micromixers, and microreactors. In this manuscript, we employ NMR in the form of a voxel-selective multiple modulation multiple echo sequence (MMMEV) to monitor average velocities in individual microchannels inside a six-channel network. The technique produces average velocities which are consistent with the imposed flow rates. In addition, we take advantage of the short acquisition time (32 ms per velocity component) of the technique to quantitatively track the time evolution of the fluid velocity in a pulsatile flow phantom.

Algorithms↗
PubMed2005

Parallel imaging for NMR microscopy at 14.1 Tesla.

Parallel imaging techniques using arrays of mutually decoupled coils have become standard on almost all clinical imaging systems. Such techniques also have great potential for high-field magnetic resonance (MR) microscopy, where measurement times are usually long and susceptibility artifacts can be severe. However, it is technically very challenging to design efficient high-frequency phased arrays for small-diameter, vertical-bore magnets, especially since standard decoupling methods, such as impedance mismatched preamplifiers, cannot be easily integrated. A four-coil phased array was constructed for microimaging at 600 MHz, and sensitivity encoding (SENSE) and generalized autocalibrating partially parallel acquisitions (GRAPPA) reconstructions of spin-echo and echo-planar images of the mouse brain were performed to reduce imaging time and susceptibility artifacts, respectively.

Algorithms↗
PubMed2005

Reduced data acquisition time in multi-dimensional NMR spectroscopy using multiple-coil probes.

A new hardware-based approach is presented to reduce data acquisition times in multi-dimensional NMR spectroscopy using a multiple-coil probe. Using a four-coil setup, two-dimensional COSY and TOCSY spectra were acquired in one-quarter the time of conventional spectra by simultaneous acquisition of different effective t1 evolution times for each coil. Data processing consists of simple phase-shifting and intensity normalization of the individual data sets, and results in spectra almost identical to those acquired in a conventional manner. This method can potentially be integrated with other new data acquisition and processing schemes for further increases in data acquisition speed.

Chloroquine↗
PubMed2004

Characterization of the physicochemical parameters of dense core atrial gland and lucent red hemiduct vesicles in Aplysia californica.

Characterizing femtoliter-volume cellular organelles requires innovative analytical techniques such as mass spectrometry, separations, and NMR. The capabilities of all three are demonstrated for characterizing the physicochemical properties of the electron-dense core atrial gland vesicles from Aplysia californica and comparing them with the same properties of the electron lucent red hemiduct vesicles. Single-vesicle mass spectrometric measurements show that the atrial gland vesicles contain an abundance of peptides while the red hemiduct vesicles contain no detectable peptide signals. Capillary electrophoresis with wavelength-resolved native fluorescence detection is used to characterize larger vesicle samples for tyrosine- and tryptophan-containing peptides. Using NMR spectroscopy, we show that the physiologically active peptides located in the core of the atrial gland vesicles are NMR inactive when the vesicles are intact. Resonances from these peptides appear after vesicle lysis by heating, suggesting that initially they are packed in a crystalline or semicrystalline core so that the NMR resonances are not detectable. In contrast, the red hemiduct vesicles appear to have their contents stored in a completely mobile form due to the fact that no new NMR resonances are detected after heating.

Animals↗
PubMed2004

Signal enhancement by diffusion: experimental observation of the "DESIRE" effect.

Inadequate signal-to-noise ratio is a major factor limiting applications of magnetic resonance microscopy. The "Diffusion Enhancement of Signal and Resolution" (DESIRE) scheme promises potential sensitivity enhancements of between one and three orders of magnitude, but images using this mechanism have not been shown to date. Here, we report the first images obtained using the DESIRE method, and obtain excellent agreement between numerical simulations and experimental data with signal-to-noise enhancements of close to one order of magnitude.

Magnetic Resonance Spectroscopy↗