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Indium tin oxide (ITO) thin films were deposited on polyethylene napthalate (PEN) by rf sputtering using different rf powers (60 and 120 W) and at different substrate temperatures (room temperature and 100 °C). Rutherford backscattering spectrometry was used to determine the oxygen content in the films. Hall effect measurements were used to evaluate the electrical properties. In this paper the influence of defect structure, sputtering conditions, and the effect of annealing on the electrical and optical properties of ITO on PEN have been investigated. Electrical properties such as carrier concentration, mobility, and resistivity of the ITO films varied with rf power and substrate temperature. The electricalproperties of the films changed after annealing in air. This study also describes how the as-deposited amorphous ITO changes from amorphous to crystalline as a result of heat treatment, and investigates the effects of Sn defect clustering on electrical and optical properties of the ITO films.
The construction of short pulse (<200 fs) tunable X-ray
laser sources based on the X-ray free electron laser (XFEL)
concept will be a watershed for plasma-based and warm dense
matter research. These new fourth generation light sources will
have extremely high fields and short wavelengths (∼0.1 nm)
with peak spectral brightnesses 1010 greater than
third generation sources. Further, the high intensity upgrade
of the GSI accelerator facilities will lead to specific energy
depositions up to 200 kJ/g and temperatures between 1 and
10 eV at almost solid-state densities, enabling interesting
experiments in the regime of nonideal plasmas, such as the
evolution of intense ion beams in the interior of a Jovian planet.
Below we discuss several applications: the creation of warm dense
matter (WDM) research, probing of near solid density plasmas, and
laser–plasma spectroscopy of ions in plasmas. The study of
dense plasmas has been severely hampered by the fact that laser-based
methods have been unavailable and these new fourth generation sources
will remove these restrictions.
Recent experiments undertaken at the Rutherford Appleton
Laboratory to produce X-ray lasing over the 5–30 nm
wavelength range are reviewed. The efficiency of lasing is
optimized when the main pumping pulse interacts with a preformed
plasma. Experiments using double 75-ps pulses and picosecond
pulses superimposed on 300-ps background pulses are described.
The use of travelling wave pumping with the approximately
picosecond pulse experiments is necessary as the gain duration
becomes comparable to the time for the X-ray laser pulse to
propagate along the target length. Results from a model taking
account of laser saturation and deviations from the speed of
light c of the travelling wave and X-ray laser group velocity
are presented. We show that X-ray laser pulses as short as
2–3 ps can be produced with optical pumping pulses of
We present a detailed and comprenhensive theoretical investigation of the sulphur-passivated (001) surface of InP. First, the ground-state structure is determined using density-functional methods, including full relaxation of the surface. The lowest-energy structure at 0 K is a striking (2 × 2) reconstruction with the S atoms displaced from the bridge sites to form short and long dimers, belonging to two distinct sublayers. This surface structure is used to calculate the backscattering Raman spectrum; the two peaks arising from surface-layer vibrations predicted by our calculations are observed. Next, our first-principles calculations are extended to the study of a number of other stable states of the surface that can arise upon annealing. For this purpose, we construct and relax several higher-energy states of the surface, and calculate the corresponding core-level photoemission spectra. A remarkable sequence of structures is found to unfold from the fully S-covered ground state as they become energetically accessible. The surface S atoms exchange with bulk P atoms, forming new (and strong) S-P bonds while dissociating pre-existing S–S dimers. The predicted core-level spectra are found to be entirely consistent with the experimental measurements; our calculations indicate that the annealed (at about 700 K) surface is a (2 × 2) structure containing two S and two P atoms per unit cell. Finally, we have used the predicted stable surface structures to calculate the photoemission and inverse photoemission spectra. They are found to agree well with experiment if the surface is assumed to consist of a mixture of the above ground-state and annealed structures.
Metastable phase formation under highly non-equilibrium thermodynamic conditions within high-energy particle tracks are investigated. In particular, the possible formation of diamond by heavy-ion irradiation of graphite at ambient temperature is examined. This work was motivated, in part, by an earlier study which discovered nanometer-grain polycrystalline diamond aggregates of submicron-size in uranium-rich carbonaceous mineral assemblages of Precambrian age. It was proposed that these diamonds were formed within the particle tracks produced in the carbonaceous minerals by the radioactive decay of uranium. To test the hypothesis that nanodiamonds can form by ion irradiation, fine-grain polycrystalline graphite sheets were irradiated with 400 MeV Kr ions to low fluence (6 × 1012 ions-cm−2). The ion-irradiated (and unirradiated control) graphite were then subjected to acid dissolution treatments to remove the graphite and isolate any diamonds that were produced. These acid residues were characterized by transmission electron microscopy. The acid residue of the ion-irradiated graphite was found to contain nanodiamonds (at several ppm of bulk), demonstrating that ion irradiation of graphite at ambient temperature can produce diamond.
Recombining plasmas produced by picosecond laser pulses are characterized by measuring ratio of intensities of resonance lines of H- and He-like ions in the plasmas. It is found that the rapidly recombining plasmas produced by picosecond laser pulses are suitable for highgain operation.
Secondary (symptomatic) narcolepsy is rare. We report a subependymoma of the fourth ventricle associated with narcolepsy. The patient was a 50-year-old woman with a long history of narcolepsy who died of colonic carcinoma with no cerebral metastasis. She was positive for HLA-DR2. At autopsy there was a tumour dorsal to the fourth ventricle which involved the midbrain tectum and rostral pons. Histologic examination of the tumour confirmed it to be a subependymoma.
Review of the previous cases of secondary narcolepsy was made with particular reference to the anatomical location of the lesions.
Most of the lesions were found around the third ventricle and rostral brainstem.
Knowing the anatomical localization of the pathological changes in secondary narcolepsy could be important in improving our understanding of its pathogenesis.
Human exposure to lead may induce a variety of adverse effects on health including haematological, neurobehavioural, cardiovascular and renal changes and therefore continues to be a public health concern (Needleman 1989). Lead is dispersed in the environment from where it may be inhaled or ingested by man. Environmental exposure may arise from a number of potential sources: typically industrial emissions, exhaust from petrol engines, drinking water, foodstuffs, paint, soldered cans, lead glazed earthenware, dust and soil. A further source is tobacco smoke.
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