3,893 research outputs found
Ge growth on ion-irradiated Si self-affine fractal surfaces
We have carried out scanning tunneling microscopy experiments under ultrahigh
vacuum condition to study the morphology of ultrathin Ge films eposited on
pristine Si(100) and ion-irradiated Si(100) self-affine fractal surfaces. The
pristine and the ion-irradiated Si(100) surface have roughness exponents of
alpha=0.19+/-0.05 and alpha=0.82+/-0.04 respectively. These measurements were
carried out on two halves of the same sample where only one half was
ion-irradiated. Following deposition of a thin film of Ge (~6 A) the roughness
exponents change to 0.11+/-0.04 and 0.99+/-0.06, respectively. Upon Ge
deposition, while the roughness increases by more than an order of magnitude on
the pristine surface, a smoothing is observed for the ion-irradiated surface.
For the ion-irradiated surface the correlation length xi increases from 32 nm
to 137 nm upon Ge deposition. Ge grows on Si surfaces in the Stranski-Krastanov
or layer-plus-island mode where islands grow on a wetting layer of about three
atomic layers. On the pristine surface the islands are predominantly of square
or rectangular shape, while on the ion-irradiated surface the islands are
nearly diamond shaped. Changes of adsorption behaviour of deposited atoms
depending on the roughness exponent (or the fractal dimension) of the substrate
surface are discussed.Comment: 5 pages, 2 figures and 1 tabl
A new study of shower age distribution in near vertical showers by EAS air shower array
The air shower array has been developed since it started operation in 1931. The array covering an area of 900 sq m now incorporates 21 particle density sampling detectors around two muon magnetic spectrographs. The air showers are detected in the size range 10 to the 4th power to 10 to the 6th power particles. A total of 11000 showers has so far been detected. Average values of shower age have been obtained in various shower size ranges to study the dependence of shower age on shower size. The core distance dependence of shower age parameter has also been analyzed for presentation
Laser phase modulation approaches towards ensemble quantum computing
Selective control of decoherence is demonstrated for a multilevel system by
generalizing the instantaneous phase of any chirped pulse as individual terms
of a Taylor series expansion. In the case of a simple two-level system, all odd
terms in the series lead to population inversion while the even terms lead to
self-induced transparency. These results also hold for multiphoton transitions
that do not have any lower-order photon resonance or any intermediate virtual
state dynamics within the laser pulse-width. Such results form the basis of a
robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted
Formulation and evaluation of transdermal delivery system of an anti-hypertensive drug
oai:ojs2.japtronline.com:article/1The present study was aims to formulate and evaluate transdermal drug delivery for sustained release of
an anti-hypertensive drug Captopril, it is considered as drug of choice in anti hypertensive therapy and is
reported for potential administration through transdermal route. The investigation was carried out to
study the effect of different proportion of ethyl cellulose and PVP a hydrophobic and hydrophilic
polymer respectively. Transdermal patches were prepared using different combination of the two
polymers by solvent evaporation technique. Polyvinyl alcohol was used to prepare the backing
membrane and dibutyl phthalate as a plasticizer. Several Physicochemical parameter like moisture
content, moisture loss, thickness, film folding endurance, tensile strength, flatness were studied. For all
the formulations, in vitro drug release was studied using modified diffusion cell. Formulations with
highest proportion of polyvinyl pyrolidone shows faster release whereas increasing proportion of ethyl
cellulose produces a prolonged regimen of sustained drug delivery through transdermal route for a
period of 24 hrs
Nanoscale self-affine surface smoothing by ion bombardment
The topography of silicon surfaces irradiated by a 2-MeV Si+ ion beam at normal incidence and ion fluences in the range 1015-1016ions/cm2 has been investigated using scanning tunneling microscopy. At length scales below ~50 nm, surface smoothing is observed; the smoothing is more prominent at smaller length scales. The smoothed surface is self-affine with a scaling exponent α=0.53± 0.03
Precompaction irradiation effects: Particles from an early active sun?
Two recent studies have shown that solar flare irradiated grains from Murchison and Kapoeta have excess spallogenic Ne-21 compared to unirradiated grains, indicating large precompaction particle irradiation effects. The quantity of cosmogenic neon in these grains presents serious difficulties for either galactic cosmic ray or normal solar flare sources. In the first study it was suggested that the effect might be the result of exposure to an early active sun. The more recent experiment both confirms the earlier results and provides constraints on the characteristic energy spectrum on the irradiation. The first results were obtained from Murchison olivines and Kapoeta pyroxenes by mass spectrometric analysis of sets of grains selected on the basis of the presence or absence of solar flare particle tracks. In the second work plagioclase feldspar grains from Kapoeta were studied
Evidence in meteorites for an active early Sun
The amounts of neon-21 found in meteorite particles indicate that the Sun experienced a period of intense solar flare activity approximately 4.5 billion years ago
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