An expansion of the field modulus suitable for the description of strong field gradients in axisymmetric magnetic fields: Application to single-sided magnet design, field mapping and STRAFI

International audienceMapping (or plotting) the magnetic field has a critical importance for the achievement of the homogeneous magnetic field necessary to standard MR experiments. A powerful tool for this purpose is the Spherical Harmonic Expansion (SHE), which provides a simple way to describe the spatial variations of a field in free space. Well-controlled non-zero spatial variations of the field are critical to MRI. The resolution of the image is directly related to the strength of the gradient used to encode space. As a result, it is desirable to have strong variations of the field. In that case, the SHE cannot be used as is, because the field modulus variations are affected by the variations of all components of the field. In this paper, we propose a method based on the SHE to characterize such variations, theoretically and experimentally, in the limit of an axisymmetric magnetic field. Practical applications of this method are proposed through the examples of single-sided magnet design and characterization, along with Stray-Field Imaging (STRAFI)

Approche psychanalytique de la psychose : structure, logique, clinique, éthique

For Freud and Lacan psychosis is not a deficiency. Nowadays, Schreber’s text still remains an unequalled paradigmatic treatise. For Freud, paranoid delirium is an attempt at recovery, and for Lacan it is an attempt to analyze severe logic. The thorny question of psychotic transference still remains. Freud does not believe that a psychotic patient is capable of analytical transference. Lacan thinks that at the beginning, the transference is likely to provoke a trigged of, furthermore the psychotic has the object a in his pocket. Freud continued seeing psychotic patients even though he dissuaded his students from doing so. Lacan, who psychosis before psychoanalysis, suggests that the analyst should not draw back in the face of psychosis. Can the psychotic subject, which stays out of every social bond established, be received by analytical speech? This is what we examine throughout the thesis. If the subject is not cured of his psychosis, can he invent substitutes within the treatment in order to deal with it? Thus, there is no general solution but rather a contingency approach which can betaken. There is no guarantee but there might be the analyst’s desire…Pour Freud et Lacan, la psychose n'est pas un état déficitaire. Le texte de Schreber demeure un traité paradigmatique, aujourd'hui encore inégalé.Le délire paranoïaque est une tentative de guérison pour le premier. Un essai de rigueur pour le second. Reste la question épineuse du transfert psychotique. Freud ne croit pas le psychotique capable de transfert analytique, Lacan pense au début que le transfert est susceptible de provoquer un déclenchement, et que, par ailleurs, le psychotique a l'objet a dans sa poche. Freud continua à recevoir des psychotiques tout en dissuadant ses disciples de le faire. Lacan, qui connut la psychose avant la psychanalyse, avance que le psychanalyste ne doit pas reculer devant la psychose. Le sujet psychotique qui reste en dehors de tout lien social établi peut-il être accueilli par le discours analytique ? C'est cela que nous examinons dans cette thèse. Si le sujet ne guérit pas de sa psychose, peut-il inventer dans la cure des suppléances pour y faire face ? Il n’existe pas de solution générale, mais une approche des contingences. Pas de garantie donc, mais peut-être le désir de l'analyste

Simple method for the generation of multiple homogeneous field volumes inside the bore of superconducting magnets

International audienceStandard Magnetic Resonance magnets produce a single homogeneous field volume, where the analysis is performed. Nonetheless, several modern applications could benefit from the generation of multiple homogeneous field volumes along the axis and inside the bore of the magnet. In this communication, we propose a straightforward method using a combination of ring structures of permanent magnets in order to cancel the gradient of the stray field in a series of distinct volumes. These concepts were demonstrated numerically on an experimentally measured magnetic field profile. We discuss advantages and limitations of our method and present the key steps required for an experimental validation

Time-resolved, optically detected NMR of fluids at high magnetic field

International audienceWe report on the use of optical Faraday rotation to monitor the nuclear-spin signal in a set of model $^{19}$F- and $^1$H-rich fluids. Our approach integrates optical detection with high-field, pulsed NMR so as to record the time-resolved evolution of nuclear-spins after rf excitation. Comparison of chemical-shift-resolved resonances allows us to set order-of-magnitude constrains on the relative amplitudes of hyperfine coupling constants for different bonding geometries. When evaluated against coil induction, the present detection modality suffers from poorer sensitivity, but improvement could be attained via multipass schemes. Because illumination is off-resonant i.e., the medium is optically transparent, this methodology could find extensions in a broad class of fluids and soft condensed matter systems

Microbobines et RMN en phase solide

National audienceThis PhD thesis, at the interface between chemistry and physics, uses Solid State Nuclear Magnetic Resonance (ssNMR) for both exploiting diversity of materials and developing new easy-to-implement methodologies.ssNMR has proved to be really efficient to study materials and especially their interface by precisely characterising chemical environment of studied nuclei [1]. However, the main drawback of this technique is its lack of sensitivity, each analysis requiring 30 to 400 mg of sample. Such an amount is particularly difficult to obtain for sol-gel thin-film layers or for biological studies like Kidney stones.In order to solve this issue, the MACS (Magic Angle Coil Spinning) technique has been recently developed [2]. It consists of a micro-scaled coil surrounding a capillary containing the sample. Only 30 to 100 µg of material is necessary. As the microcoil is placed inside the usual solid state NMR rotor, no probe modification is needed.[1] C. Bonhomme, C. Gervais, and D. Laurencin, “Recent NMR developments applied to organic–inorganic materials,”Progress in Nuclear Magnetic Resonance Spectroscopy, vol. 77, pp. 1–48, Feb. 2014.[2] D. Sakellariou, G. L. Goff, and J.-F. Jacquinot, “High-resolution, high-sensitivity NMR of nanolitre anisotropic samples by coil spinning,” Nature, vol. 447, no. 7145, pp. 694–697, Jul. 2007

GRDD: A Dataset for Greek Dialectal NLP

In this paper, we present a dataset for the computational study of a number of Modern Greek dialects. It consists of raw text data from four dialects of Modern Greek, Cretan, Pontic, Northern Greek and Cypriot Greek. The dataset is of considerable size, albeit imbalanced, and presents the first attempt to create large scale dialectal resources of this type for Modern Greek dialects. We then use the dataset to perform dialect idefntification. We experiment with traditional ML algorithms, as well as simple DL architectures. The results show very good performance on the task, potentially revealing that the dialects in question have distinct enough characteristics allowing even simple ML models to perform well on the task. Error analysis is performed for the top performing algorithms showing that in a number of cases the errors are due to insufficient dataset cleaning

The Role of Adiponectin and BNP in Predicting Cardiovascular Events

Adiponectin and brain natriuretic peptide (BNP) are hormones released from adipocytes and myocardial cells respectively, in response to different stimuli. Adiponectin is the most abundant adipokine secreted by adipose tissue that may couple regulation of insulin sensitivity with energy metabolism. [1] Decreased plasma concentration has been observed in patients with diabetes, metabolic syndrome and coronary artery disease, and this may play a key role in the development of insulin resistance. The exact mechanism underlying anti???inflammatory properties of adiponectin is not yet well understood but there is evidence that its properties may be related, in part, to its ability to stimulate production of nitric oxide (NO), which is considered to be the potent vasodilator substance produced from endothelial cells. [2] Nowadays, adiponectin is increasingly recognized to be both a potential biomarker for the metabolic syndrome and a possible therapeutic target for the treatment of cardiovascular disease.Brain natriuretic peptide is one of the three major natriuretic peptides, atrial natriuretic peptide (ANP), B ??? type natriuretic peptide (BNP) and C ??? type natriuretic peptide (CNP), all of which share a common 17 ??? amino ??? acid ring structure and have cardioprotective actions against volume overload. [3] Although this peptide was called brain (B ??? type) natriuretic peptide (BNP), the primary site of BNP synthesis is the ventricular myocardium. [4] Its initial diagnostic value was attributed in its ability to distinguish heart failure from other causes of dyspnea. Moreover, recently BNP and NT???proBNP have been related to other cardiac diseases, such as stable and unstable angina, valvular heart disease and sudden death, adding a new angle in their diagnostic and prognostic roles. In this review, the prognostic role of adiponectin and BNP in cardiovascular diseases will be briefly presented