Search results for "Circulation"
showing 10 items of 1137 documents
Simultaneous recording of skin blood pulsations at different vascular depths by multiwavelength photoplethysmography.
2007
A new technique for parallel recording of reflection photoplethysmography (PPG) signals in a broad spectral band (violet to near-infrared) has been developed, and its potential for assessment of blood microcirculation at various depths from the skin surface is discussed. PPG signals have been simultaneously detected at cw laser wavelength sets comprising 405, 532, 645, 807, and 1064 nm. Various signal baseline responses to breath holding and different shapes of the PPG pulses originated from the same heartbeat but recorded at different wavelengths have been observed, indicating a depth variety of the skin blood pulsation dynamics.
The effects of linearly increasing flip angles on 3D inflow MR angiography
1994
As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP s…
Novel metallic iron/manganese-zinc ferrite nanocomposites prepared by microwave hydrothermal flash synthesis
2011
8 Caillot, T. Pourroy, G. Stuerga, D.; Metallic iron (alpha-Fe)/manganese-zinc ferrite (Fe3-x-yMnxZnyO4) nanocomposites have been successfully synthesized for the first time using microwave hydrothermal treatment of alcoholic solutions of chloride precursors and sodium ethoxide. This new type of nanocomposites, never obtained by conventional synthesis, can now be produced in a short period (e.g. 15s). The powders were characterized by X-ray diffraction, transmission electron microscopy and magnetic properties were measured. In most cases, three classes of crystallites were observed; one of them is composed of grains of about 100 nm in size where the metal is inserted into the oxide. For all…
Hydrothermal Processing for Increasing the Hydroxyl Ion Concentration in Hydroxyl Depleted Hydroxyapatite
2018
Thermal spraying is commercially used to produce hydroxyapatite coatings, but the high temperature depletes hydroxyl ions in the structure. To return hydroxyapatite to its original state, it is necessary to restore the hydroxyl ion content in the structure. In this work, the effect of hydrothermal treatment on the hydroxyl ions was investigated in hydroxyapatite powder and thermally sprayed hydroxyapatite coatings. Samples were hydrothermally treated at 200 °C for 24 h and 48 h. Chemical phases were determined by X-ray diffraction, functional groups and hydroxyl ion concentration was examined by Fourier transform infra-red spectroscopy. Results showed that hydrothermal processing of hydroxy…
Effect of hydrothermal ageing on the thermal and delamination fracture behaviour of CFRP composites
2014
Abstract This work investigates the hydrothermal ageing behaviour of a carbon fibre reinforced laminate and its epoxy matrix in bulk conditions. A model DGEBA epoxy is employed, and water uptake and dynamic mechanical thermal (DMTA) analyses have been performed on both the composites and bulk resin. Fracture toughness of the bulk resin has been measured, evidencing a substantially unmodified critical stress intensity factor KIC, although the evidence of plasticisation effects given by DMTA. Interlaminar Mode I fracture toughness of the composite showed a variable trend towards slight decreases or slight increases, according to the prevailing toughening or embrittling mechanisms activated by…
Regional blood flow in deep structures of the brain measured in acute cat experiments by means of a new beta-sensitive semiconductor needle detector.
1967
Regional cerebral blood flow was measured by means of isotope clearance with a new type of solid state beta-sensitive needle detector (diameter 0.9 mm) introduced into the brain tissue in acute cat experiments. The flow values obtained within the cortex were compared with values recorded above the same cortical region with the same needle detector, or with a small GM-tube. The insertion of the needle detector into the brain tissue gave rise to injury (checked histologically) which deformed the clearance curves in a manner suggesting that the normal circulation had been destroyed within the tissue from which the measurements were made.
Hydrothermal synthesis of nanostructured zirconia materials: Present state and future prospects
2005
Abstract Hydrothermal procedures for the synthesis of zirconia-doped nanocrystalline powders show important advantages from the thermodynamic and kinetic point of view (larger domain stability of solid species, faster kinetics crystallisation) as well as from technological point of view (one-step synthesis process at low temperatures, better control of the crystallisation and grain sizes with possibilities to obtain nanocrystalline materials, versatility, environmental friendly technology). Establishment of the conditions for obtaining ZrO2-doped with different oxides is based on thermodynamic predictions. Kinetic modelling of the hydrothermal synthesis of zirconia nanopowders is presented.…
Synthesis of a Hydrothermally Stable, Periodic Mesoporous Material Containing Magnetite Nanoparticles, and the Preparation of Oriented Films
2006
Magnetite nanoparticles modified covalently with triethoxysilane having a quaternary dicetyl ammonium ion are used together with tetraethylorthosilicate as building blocks to prepare a mesoporous material. Cetyltrimethylammonium bromide is used as a structure-directing agent under conditions typically used for mesoporous MCM-41 silicas. The resulting mesoporous material (MAG-MCM-41), containing up to 15 wt % of magnetite is characterized by transmission electron microscopy (TEM), isothermal gas adsorption, and X-ray diffraction. In contrast to siliceous MCM-41, mesoporous MAG-MCM-41 exhibits a remarkable hydrothermal stability. The magnetic properties of MAG-MCM-41 are characterized by DC a…
Synthesis of self-assembled α-GaOOH microrods and 3D hierarchical architectures with flower like morphology and their conversion to α-Ga2O3
2015
Abstract This report reveals the methodology for the fabrication of α-GaOOH micro rods and micro flowers from gallium nitrate with two different complexing agents. α-GaOOH self-assembled 3D hierarchical architecture, comprising of nanorods and nanoribbbons with a flower like morphology, is fabricated under benign hydrothermal conditions. Calcination of α-GaOOH results in formation of α-Ga 2 O 3 with the retention of morphology. Both gallium oxyhydroxide and gallium oxide microstructures were analyzed with SEM, EDX, TEM and powder X-ray diffraction. α-Ga 2 O 3 micro flowers are furnished with nanorods having ordered diamond like cross section with a diagonal length proportion of 2:1. The hyd…
Effect of surface impurities on downconversion luminescence of Pr3+, Yb3+ activated SrF2 nanoparticles
2020
Abstract Pr3+,Yb3+ activated SrF2 nanoparticles synthesized by low-temperature hydrothermal method were studied. The composition and size of nanoparticles were intentionally changed by controlling synthesis conditions. After structural and morphological characterization, the spectroscopic properties of the nanoparticles were analyzed in the visible and near infrared spectra ranges. The results show correlation between the gradual change of the amount of carboxylate and hydroxyl moieties on the nanoparticle surface, varied by the size nanoparticles and the quenching of the luminescence. The size-related amount of surface quenchers is strongly connected to the decrease of the downconversion e…