91 research outputs found
Characterization of Flexible RF Microcoil Dedicated to Surface Mri
In Magnetic Resonance Imaging (MRI), to achieve sufficient Signal to Noise
Ratio (SNR), the electrical performance of the RF coil is critical. We
developed a device (microcoil) based on the original concept of monolithic
resonator. This paper presents the used fabrication process based on
micromoulding. The dielectric substrates are flexible thin films of polymer,
which allow the microcoil to be form fitted to none-plane surface. Electrical
characterizations of the RF coils are first performed and results are compared
to the attempted values. Proton MRI of a saline phantom using a flexible RF
coil of 15 mm in diameter is performed. When the coil is conformed to the
phantom surface, a SNR gain up to 2 is achieved as compared to identical but
planar RF coil. Finally, the flexible coil is used in vivo to perform MRI with
high spatial resolution on a mouse using a small animal dedicated scanner
operating at in a 2.35 T.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Carbon nanotubes allow capture of krypton, barium and lead for multichannel biological X-ray fluorescence imaging
The desire to study biology in situ has been aided by many imaging techniques. Among these, X-ray fluorescence (XRF) mapping permits observation of elemental distributions in a multichannel manner. However, XRF imaging is underused, in part, because of the difficulty in interpreting maps without an underlying cellular âblueprintâ; this could be supplied using contrast agents. Carbon nanotubes (CNTs) can be filled with a wide range of inorganic materials, and thus can be used as âcontrast agentsâ if biologically absent elements are encapsulated. Here we show that sealed single-walled CNTs filled with lead, barium and even krypton can be produced, and externally decorated with peptides to provide affinity for sub-cellular targets. The agents are able to highlight specific organelles in multiplexed XRF mapping, and are, in principle, a general and versatile tool for this, and other modes of biological imaging
Multivariate discovery and replication of five novel loci associated with Immunoglobulin G <i>N</i>-glycosylation
Multivariate analysis methods can uncover the relationship between phenotypic measures characterised by modern omic techniques. Here the authors conduct a multivariate GWAS on IgG N-glycosylation phenotypes and identify 5 novel loci enriched in immune system genes
Mechanisms of relapse in acute leukaemia: involvement of p53 mutated subclones in disease progression in acute lymphoblastic leukaemia
Mutations of the p53 tumour suppressor gene are infrequent at presentation of both acute myeloblastic leukaemia (AML) and acute lymphoblastic leukaemia (ALL), being found in between 5â10% of AML and 2â3% of ALL. Here we have studied the frequency of detection of p53 mutations at relapse of both AML and B-precursor ALL. In those patients with detectable mutations at relapse we investigated whether the mutation was detectable at presentation and was thus an early initiating event or whether it had arisen as a late event associated with relapse. Bone marrow samples from 55 adults and children with relapsed AML (n = 41) or ALL (n = 14) were analysed for p53 gene alterations by direct sequencing of exons 5â9. For samples where a p53 mutation was found at relapse, analysis of presentation samples was carried out by direct sequencing of the exon involved, or by allele-specific polymerase chain reaction (PCR) if the mutation could not be detected using direct sequencing. A p53 mutated gene was found at relapse in seven out of 55 cases. The frequency was higher in relapsed ALL (four out of 14 cases; 28.6%) compared to AML (three out of 41 cases; 7.3%). In five out of the seven cases presentation samples were available to study for the presence of the mutation. In two out of two AML patients the p53 mutation was detectable in the presentation sample by direct sequencing. In three ALL patients analysis of presentation material by direct sequencing showed a small mutant peak in one case, the other two being negative despite the sample analysed containing > 90% blast cells. However in both of these patients, the presence of p53 mutation was confirmed in the presentation sample using allele-specific PCR. In one of these patients the emergence of a subclone at relapse was confirmed by clonality analysis using IgH fingerprinting. Our results confirm that in ALL p53 mutations are present in a proportion of patients at relapse. Furthermore cells carrying the mutation are detectable at presentation in a minor clone suggesting that p53 mutations in ALL may be a mechanism contributing to disease relapse. © 1999 Cancer Research Campaig
RF characterization of intracellular microalgae lipids
This work presents an original approach to sense the lipid intracellular content of microalgae, by the Radio Frequency (RF) dielectric spectral characterization of these unicellular organisms. To do so, a "homemade" open-ended coaxial sensor was associated to a Vector Network Analyzer (VNA), which allowed a broadband characterization in the frequency range from 30MHz to 3GHz. The sensor combines a coaxial line with a modified SMA connector. This study shows that the lipid quantification can be determined with the complex dielectric spectra properties extracted from the reflection coefficient (S) measurement. A calibration of the open-ended coaxial probe is performed by using three different conditions (vacuum, water, methanol) from which the complex dielectric behavior is mastered. A model inversion is finally achieved to estimate the complex permittivity spectrum of the biological samples in a large frequency range, which is related to the microalgae lipid content
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