Electron transport properties of irradiated polyimide thin films in single track regime.

We have prepared a suite of polyimide thin films containing spatially separated one-dimensional conductive-nanowires by ion-beam irradiation exhibiting temperature dependent electrical resistance consistent with thermally activated electron hopping with activation energies about 1 eV arising from localized states spatially distributed along the ion tracks. Dielectric measurements showed the formation of high dielectric constant interphase regions surrounding each ion track generated during the irradiation process, responsible for space-charge accumulation which influences electron transport within the ion tracks. This behavior suggests a role for space-charge effects and dielectric properties in this interphase region in the control of electron transport within single track nanowires. © 2009, American Institute of Physic

Precipitation of rutile and anatase (Tio12) fine powders and their conversion to MTiO3 (M = Ba, Sr, Ca) by the hydrothermal method

Fine powders of TiO2 (rutile) with high degree of crystallinity are formed from aqueous titanium oxychloride solution under hydrothermal conditions at 160–230°C and 15–100 kg/cm2 for 1–2 hours. The anatase phase is produced from the same medium when sulfate ion impurity is present, with Image . Both these fine powders are converted to BaTiO3, SrTiO3 or CaTiO3 when suspended in Ba(OH)2 or Sr(OH)2 solution or in an aqueous slurry of carbonate-free CaO with Image , at 180–280°C and 12–65 kg/cm2 for 4–8 hours. The resulting fine powders contain monocrystallites of the perovskite phase with 0.1–1.5 μm particle size

Probing the structure of nanochannal arrays by electrostatic force microscopy

Electrostatic force microscopy (EFM) represents a versitile tool for the characterisation of electric and dielectric structures at nanoscale which can be employed to provide charge distributions associated with such nanotopologies. EFM-phase profiles show only the variation of electrostatic force which is strongly influenced by the surface conductivity of nanostructured arrays providing improved definition compared to conventional AFM. Here we apply it to carbon nanochannel arrays embedded within polyimide dielectric matrices. Copyright © 2012 World Scientific Publishing Co. All rights reserve

Thermal modelling of a differential calorimeter for magnetic nanoparticle specific absorption rate measurement

Magnetic nanoparticles provide thermo-necrosis therapies but the impact of temperature on the surrounding tissue must be precisely controlled to avoid damage. In this paper, we investigated the design and validation of a differential calorimeter for the evaluation of the specific absorption rate (SAR) of magnetic nanoparticles within colloidal dispersions. Accuracy in the final SAR values was achieved through systematic analysis of the key sources of thermal energy inputs and thermal transport within the environment of the calorimeter, modelled by both a distributed heat equation and a lumped parameter model. This design and the two thermal capacity models used allowed subsequent experimental parameters to be evaluated from the calorimetry protocol reducing uncertainty in the SAR values. Enhanced precision in SAR values would provide additional control of tissue temperatures in thermal necrosis when employing magnetic nanoparticles as a heating source

Formation of energetic heavy ion tracks in polyimide thin films

Polyimide thin films have been irradiated with a high energy beam of heavy ions to a fluence of approximately 4 × 1013 ions/cm2. Proton backscattering spectroscopy was used to measure the composition of the films, which showed that oxygen was the element that exhibited the most rapid loss from the film. The gases evolved from the film during polymer modification were monitored using a quadrupole mass spectrometer for residual gas analysis (RGA). The fluence dependence of RGA signals were indicative of multi-step processes of gas release, whereby the passage of an ion through a region of pristine film changes the local molecular structure to one that will more readily form volatile species when subsequent ions pass. © 2013, Elsevier B.V

The improved electromechanical sensitivity of polymer thin films containing carbon clusters produced in situ by irradiation with metal ions

Greatly enhanced electromechanical sensitivities were observed in ion beam irradiated polyimide films, where high resolution transmission electron microscopy and atomic force microscopy studies showed that 5.5 MeV Cu3+ ions produce randomly dispersed and highly oriented conducting nanochannels containing carbon clusters in polyimide with considerable overlap and narrow tunnel gap distributions between neighbouring nanochannels. Selected area electron diffraction studies confirmed the graphitic structure of these carbon clusters and also showed that the graphitic layers had preferential orientation parallel to the ion beam direction arising from relaxation of the graphitic layers within the nanochannels relieving local surface stresses in the polyimide matrix generated during irradiation as well as alignment of graphitic basal layers by volatile gases formed during irradiation escaping to the surface minimising resistance to gas flow. Electron energy loss spectroscopy also confirmed the graphitic structure of these carbon clusters within the nanochannels. Film electrical resistance increased exponentially with applied strain demonstrating the dominant role of tunnel gap modulation under strain. Gauge factors >1000 were achieved in these films at >3000 lstrains. Narrow distribution of tunnel gaps between the overlapping nanochannels is responsible for the high electromechanical sensitivities observed in these films compared to carbon nanotube-polymer (50) films

Primary hyperaldosteronism without suppressed renin: A case report

Primary Hyperaldosteronism characterizes elevated plasma and urinary aldosterone with suppression of plasma renin activity. Suppression can be due to sodium retention which is aldosterone dependent and extracellular volume expansion. Here a 29 year old male presented with uncontrolled hypertension, on work up he was diagnosed to have primary Hyperaldosteronism with normal plasma renin level. So with the available medical data on the patient as well as the publications on aldosterone/renin association in primary hyperaldosteronism was reviewed here to explain the rare finding

Electron transport in semiconducting nanoparticle and nanocluster carbon-polymer composites

The electron transport properties of two types of carbon-polyimide (C-PI) nanocomposite thin films have been evaluated. Conductive nanocomposites formed by incorporation of 30 nm carbon particles prior to polymer cross linking (ex situ formation) has been compared to high energy ion beam irradiation in situ formation of nanoscale carbon clusters within the polymer composite. Addition of carbon nanoparticles were able to reduce the resistivity by 13 orders of magnitude for 8 vol% carbon content. The irradiated in situ formed film showed a comparable resistivity to this 8% C-PI film. All the films exhibited negative temperature coefficient of resistance (NTCR) behaviour. While in the ex situ films the NTCR decreased progressively with increasing temperature above 350 K, the in situ film exhibited a constant NTCR value at ambient as well as elevated temperatures indicating that films formed by ion beam irradiation eliminate possible clustering of nanoparticles prior to crosslinking seen in the ex situ films. The optimum hop energies for the ex situ films ranged from 23.1 to 8.05 meV when carbon content increased from 1 to 8 vol% and the corresponding value for the in situ formed film was 34.94 meV. These films had appreciable NTCR values, and were evaluated for their thermistor behaviour as a class of material with potential for temperature sensing devices

Caractéristiques de la prééclampsie et lésions placentaires (étude rétrospective d'une série de 194 cas)

LILLE2-BU Santé-Recherche (593502101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

The Nd–Mn exchange interaction in Nd

The Nd-Mn exchange interaction in Nd0.7Sr0.3MnO3 is considered by studying its influence on the Mn-55 spin-echo NMR lineshape and spin- spin relaxation time. It is seen that the interaction is of considerable strength well above the Nd spin ordering temperature (approximate to 20 K), with a significant influence on the Mn (electron) spin dynamics