1,275 research outputs found
Polymer Dissolution Model: An Energy Adaptation Of The Critical Ionization Theory
The current scale of features size in the microelectronics industry has reached the point where molecular level interactions affect process fidelity and produce excursions from the continuum world like line edge roughness (LER). Here we present a 3D molecular level model based on the adaptation of the critical ionization (CI) theory using a fundamental interaction energy approach. The model asserts that it is the favorable interaction between the ionized part of the polymer and the developer solution which renders the polymer soluble. Dynamic Monte Carlo methods were used in the current model to study the polymer dissolution phenomenon. The surface ionization was captured by employing an electric double layer at the interface, and polymer motion was simulated using the Metropolis algorithm. The approximated interaction parameters, for different species in the system, were obtained experimentally and used to calibrate the simulated dissolution rate response to polymer molecular weight and developer concentration. The predicted response is in good agreement with experimental dissolution rate data. The simulation results support the premise of the CI theory and provide an insight into the CI model from a new prospective. This model may provide a means to study the contribution of development to LER and other related defects based on molecular level interactions between distinct components in the polymer and the developer.Chemical Engineerin
Combined analysis of solar neutrino and solar irradiance data: further evidence for variability of the solar neutrino flux and its implications concerning the solar core
A search for any particular feature in any single solar neutrino dataset is
unlikely to establish variability of the solar neutrino flux since the count
rates are very low. It helps to combine datasets, and in this article we
examine data from both the Homestake and GALLEX experiments. These show
evidence of modulation with a frequency of 11.85 yr-1, which could be
indicative of rotational modulation originating in the solar core. We find that
precisely the same frequency is prominent in power spectrum analyses of the
ACRIM irradiance data for both the Homestake and GALLEX time intervals. These
results suggest that the solar core is inhomogeneous and rotates with sidereal
frequency 12.85 yr-1. We find, by Monte Carlo calculations, that the
probability that the neutrino data would by chance match the irradiance data in
this way is only 2 parts in 10,000. This rotation rate is significantly lower
than that of the inner radiative zone (13.97 yr-1) as recently inferred from
analysis of Super-Kamiokande data, suggesting that there may be a second, inner
tachocline separating the core from the radiative zone. This opens up the
possibility that there may be an inner dynamo that could produce a strong
internal magnetic field and a second solar cycle.Comment: 22 pages, 9 tables, 10 figure
Silicates in D-type symbiotic stars: an ISO overview
We investigate the IR spectral features of a sample of D-type symbiotic
stars. Analyzing unexploited ISO-SWS data, deriving the basic observational
parameters of dust bands and comparing them with respect to those observed in
other astronomical sources, we try to highlight the effect of environment on
grain chemistry and physic. We find strong amorphous silicate emission bands at
10 micron and 18 micron in a large fraction of the sample. The analysis of the
10 micron band, along with a direct comparison with several astronomical
sources, reveals that silicate dust in symbiotic stars shows features between
the characteristic circumstellar environments and the interstellar medium. This
indicates an increasing reprocessing of grains in relation to specific
symbiotic behavior of the objects. A correlation between the central wavelength
of the 10 and 18 micron dust bands is found. By the modeling of IR spectral
lines we investigate also dust grains conditions within the shocked nebulae.
Both the unusual depletion values and the high sputtering efficiency might be
explained by the formation of SiO moleculae, which are known to be a very
reliable shock tracer. We conclude that the signature of dust chemical
disturbance due to symbiotic activity should be looked for in the outer,
circumbinary, expanding shells where the environmental conditions for grain
processing might be achieved. Symbiotic stars are thus attractive targets for
new mid-infrared and mm observations.Comment: 24 pages, 6 figures, 5 tables - to be published in A
Relativistic Electron Shock Drift Acceleration in Low Mach Number Galaxy Cluster Shocks
An extreme case of electron shock drift acceleration in low Mach number
collisionless shocks is investigated as a plausible mechanism of initial
acceleration of relativistic electrons in large-scale shocks in galaxy clusters
where upstream plasma temperature is of the order of 10 keV and a degree of
magnetization is not too small. One-dimensional electromagnetic full particle
simulations reveal that, even though a shock is rather moderate, a part of
thermal incoming electrons are accelerated and reflected through relativistic
shock drift acceleration and form a local nonthermal population just upstream
of the shock. The accelerated electrons can self-generate local coherent waves
and further be back-scattered toward the shock by those waves. This may be a
scenario for the first stage of the electron shock acceleration occurring at
the large-scale shocks in galaxy clusters such as CIZA J2242.8+5301 which has
well defined radio relics.Comment: 26 pages, 10 figures, accepted for publication in Ap
Geologically constrained evolutionary geomechanical modelling of diapir and basin evolution: a case study from the Tarfaya basin, West African coast
We systematically incorporate burial history, sea floor geometry and tectonic loads from a sequential kinematic restoration model into a 2D evolutionary geomechanical model that simulates the formation of the Sandia salt diapir, Tarfaya basin, NW African Coast. We use a poro-elastoplastic description for the sediment behaviour and a viscoplastic description for the salt. Sedimentation is coupled with salt flow and regional shortening to determine the sediment porosity and strength and to capture the interaction between salt and sediments. We find that temporal and spatial variation in sedimentation rate is a key control on the kinematic evolution of the salt system. Incorporation of sedimentation rates from the kinematic restoration at a location east of Sandia leads to a final geomechanical model geometry very similar to that observed in seismic reflection data. We also find that changes in the variation of shortening rates can significantly affect the present-day stress state above salt. Overall, incorporating kinematic restoration data into evolutionary models provides insights into the key parameters that control the evolution of geologic systems. Furthermore, it enables more realistic evolutionary geomechanical models, which, in turn, provide insights into sediment stress and porosity
Noise storm continua: power estimates for electron acceleration
We use a generic stochastic acceleration formalism to examine the power
() input to nonthermal electrons that cause
noise storm continuum emission. The analytical approach includes the derivation
of the Green's function for a general second-order Fermi process, and its
application to obtain the particular solution for the nonthermal electron
distribution resulting from the acceleration of a Maxwellian source in the
corona. We compare with the power observed in noise
storm radiation. Using typical values for the various parameters, we find that
, yielding an efficiency
estimate in the range 10^{-10} \lsim \eta
\lsim 10^{-6} for this nonthermal acceleration/radiation process. These
results reflect the efficiency of the overall process, starting from electron
acceleration and culminating in the observed noise storm emission.Comment: Accepted for publication in Solar Physic
Survey on solar X-ray flares and associated coherent radio emissions
The radio emission during 201 X-ray selected solar flares was surveyed from
100 MHz to 4 GHz with the Phoenix-2 spectrometer of ETH Zurich. The selection
includes all RHESSI flares larger than C5.0 jointly observed from launch until
June 30, 2003. Detailed association rates of radio emission during X-ray flares
are reported. In the decimeter wavelength range, type III bursts and the
genuinely decimetric emissions (pulsations, continua, and narrowband spikes)
were found equally frequently. Both occur predominantly in the peak phase of
hard X-ray (HXR) emission, but are less in tune with HXRs than the
high-frequency continuum exceeding 4 GHz, attributed to gyrosynchrotron
radiation. In 10% of the HXR flares, an intense radiation of the above genuine
decimetric types followed in the decay phase or later. Classic meter-wave type
III bursts are associated in 33% of all HXR flares, but only in 4% they are the
exclusive radio emission. Noise storms were the only radio emission in 5% of
the HXR flares, some of them with extended duration. Despite the spatial
association (same active region), the noise storm variations are found to be
only loosely correlated in time with the X-ray flux. In a surprising 17% of the
HXR flares, no coherent radio emission was found in the extremely broad band
surveyed. The association but loose correlation between HXR and coherent radio
emission is interpreted by multiple reconnection sites connected by common
field lines.Comment: Solar Physics, in pres
The Pulsation of Chi Cygni Imaged by Optical Interferometry; a Novel Technique to Derive Distance and Mass of Mira Stars
We present infrared interferometric imaging of the S-type Mira star Chi
Cygni. The object was observed at four different epochs in 2005-2006 with the
IOTA optical interferometer (H band). Images show up to 40% variation in the
stellar diameter, as well as significant changes in the limb darkening and
stellar inhomogeneities. Model fitting gave precise time-dependent values of
the stellar diameter, and reveals presence and displacement of a warm molecular
layer. The star radius, corrected for limb darkening, has a mean value of 12.1
mas and shows a 5.1mas amplitude pulsation. Minimum diameter was observed at
phase 0.94+/-0.01. Maximum temperature was observed several days later at phase
1.02+/-0.02. We also show that combining the angular acceleration of the
molecular layer with CO (Delta v = 3) radial velocity measurements yields a
5.9+/-1.5 mas parallax. The constant acceleration of the CO molecules -- during
80% of the pulsation cycle -- lead us to argument for a free-falling layer. The
acceleration is compatible with a gravitational field produced by a
2.1(+1.5/-0.7) solar mass star. This last value is in agreement with
fundamental mode pulsator models. We foresee increased development of
techniques consisting in combining radial velocity with interferometric angular
measurements, ultimately allowing total mapping of the speed, density, and
position of the diverse species in pulsation driven atmospheres.Comment: 36 pages, accepted in Ap
Milestones in the Observations of Cosmic Magnetic Fields
Magnetic fields are observed everywhere in the universe. In this review, we
concentrate on the observational aspects of the magnetic fields of Galactic and
extragalactic objects. Readers can follow the milestones in the observations of
cosmic magnetic fields obtained from the most important tracers of magnetic
fields, namely, the star-light polarization, the Zeeman effect, the rotation
measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio
polarization observations, as well as the newly implemented sub-mm and mm
polarization capabilities.
(Another long paragraph is omitted due to the limited space here)Comment: Invited Review (ChJA&A); 32 pages. Sorry if your significant
contributions in this area were not mentioned. Published pdf & ps files (with
high quality figures) now availble at http://www.chjaa.org/2002_2_4.ht
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