23 research outputs found
Faceting of spherical and cylindrical monocrystals of sucrose
No full textThe experimental appearance sequence of facets of crystallographic forms on the surface of sucrose spherical monocrystals fits well the decreasing order of their absolute growth rates under the same experimental conditions. The validity of this relationship is also confirmed: (a) by experimental sphere growth from solutions doped with raffinose where the appearance sequence is inverted since the impurity inverts the order of the absolute rates; (b) by the holographic analysis of the growth of the non-polar {h0l} zone of sucrose cylindric monocrystals. Holography shows the growth fringe concentration around the spherical surface portion where the most rapid faces grow. A satisfactory interpretation of the experimental results is given on the basis of a new model which explains the growth of each single (hkl) face as the results of the two processes of step generation on the surface and normal growth at the interphase of stepped and rough surface fractions around the [hkl] pole. © 1993
Growth of sucrose crystals and tapering effect studied by Holographic interferometry
No full textEffects of dopant raffinose on the growth of sucrose crystals are studied by means of holographic interferometry. By the distibution of hologram fringes the selective doping effect is measured on (100), (110) and (1-10) forms. An interpretation is put forward for the tapering effect in the wedge shaped crystals
Abnormal end-diastolic flow pattern in the umbilical artery and perinatal mortality
No full textAbs PO05.2
Prognostic factors for survival in fetuses with reverse end-diastolic flow on Doppler umbilical artery velocimetry.
No full textAbs PO05.2
Considerations on Active Control of Crosswind Stability of Railway Vehicles
No full textThe DLR research project Next Generation Train deals with concepts, methods and technologies for a very high-speed train in double deck configuration and light-weight design. Due to these three key features crosswind stability is a particular subject of study. It is shown that conventional approaches here fall short of guaranteeing safety in high-wind occurrences according to the given homologation standards. Therefore this paper discusses the feasibility of different approaches to ensure crosswind stability by means of active control. Four different concepts are overviewed, the most promising one is then chosen und examined in detailed multibody simulations that are based on data from wind tunnel measurements of the Next Generation Train
Experimental techniques for determination of the role of diffusion and convection in crystal growth from solution
No full textVarious studies of the concentration of the solution around a growing crystal using interferometric techniques are reviewed. A holographic interferometric technique used in laboratory experiments shows that a simple description of the solution based on the assumption of a purely diffusive mechanism appears inadequate since the convection, effective even in reduced columns, always affects the growth
Measurement of liver iron overload: Noninvasive calibration of MRI-R2* by magnetic iron detector susceptometer
No full textValue of 18F-3,4-dihydroxyphenylalanine pet/mr image fusion in pediatric supratentorial infiltrative astrocytomas: A prospective pilot study
No full textInfiltrative astrocytomas (IAs) represent a group of astrocytic gliomas ranging from low-grade to highly malignant, characterized by diffuse invasion of the brain parenchyma. When compared with their adult counterpart, pediatric IAs may be considered biologically distinct entities; nevertheless, similarly to those in adults they represent a complex oncologic challenge. The aim of this study was to investigate the diagnostic role, clinical contribution, and prognostic value of fused 18F-3,4-dihydroxyphenylalanine ( 18FDOPA) PET/MR images in pediatric supratentorial IAs. Methods: Pediatric patients with supratentorial IAs involving at least 2 cerebral lobes, either newly diagnosed or with suspected disease progression, prospectively underwent 18F-DOPA PET and conventional MR imaging, performed within 10 d of each other. 18F-DOPA PET data were interpreted qualitatively and semiquantitatively, fusing images with MR images. PET scans were classified as positive if tumors identified on MR imaging exhibited tracer uptake above the level of the corresponding contralateral normal brain. Maximum standardized uptake values, tumor-to-normal contralateral tissue ratios, and tumor-to-normal striatum ratios were calculated for all tumors. Correlations between the degree and extent of 18F-DOPA uptake, MR imaging tumor characteristics, and histologic results were investigated. The contribution of 18F-DOPA PET/MR image fusion was considered relevant if it enabled one to select the most appropriate biopsy site, discriminate between disease progression and treatmentrelated changes, or influence treatment strategy. The patient's outcome was finally correlated with 18F-DOPA uptake. Results: Thirteen patients (8 boys and 5 girls) were included (5 diffuse astrocytomas, 2 anaplastic astrocytomas, 5 gliomatosis cerebri, and 1 glioblastoma multiforme). The 18F-DOPA uptake pattern was heterogeneous in all positive scans (9/13), revealing metabolic heterogeneities within each tumor. Significant differences in terms of 18F-DOPA uptake were found between low- and high-grade lesions (P<0.05). The diagnostic and therapeutic contribution of 18F-DOPA PET/MR image fusion was relevant in 9 of 13 patients (69%). 18F-DOPA uptake correlated significantly with progression-free survival (P=0.004). Conclusion: Our results indicate that 18F- DOPAPET/MRimage fusionmaybea reliable imaging biomarker of pediatric IAs. Information gathered by this combined imaging approach can be readily transferred to the everyday practice and may help clinicians to better stratify patients with IAs, especially diffuse astrocytomas and gliomatosis © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc
Integrated optimization of ascent trajectory and srm design of multistage launch vehicles
No full textThis paper presents a methodology for the concurrent first-stage preliminary design and ascent trajectory optimization, with application to a Vega-derived Light Launch Vehicle. The reuse as first stage of an existing upper-stage (Zefiro 40) requires a propellant grain geometry redesign, in order to account for the mutated operating conditions. An optimization code based on the parallel running of several Differential Evolution algorithms is used to find the optimal internal pressure law during Z40 operation, together with the optimal thrust direction and other relevant flight parameters of the entire ascent trajectory. Payload injected into a target orbit is maximized, while respecting multiple design constraints, either involving the alone solid rocket motor or dependent on the actual flight trajectory. Numerical results for SSO injection are presented
