168 research outputs found
Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 1.0 torr)
The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes
Homogeneous reactions of hydrocarbons, silane, and chlorosilanes in radiofrequency plasmas at low pressures
The ion-molecule and radical-molecule mechanisms are responsible for the dissociation of hydrocarbon, silane, and chlorosilane monomers and the formation of polymerized species, respectively, in an RF plasma discharge. In a plasma containing a mixture of monomer and argon the rate-determining step for both dissociation and polymerization is governed by an ion-molecule type of interaction. Adding hydrogen or ammonia to the monomer-argon mixture transforms the rate-determining step from an ion-molecule interaction to a radical-molecule interaction for both monomer dissociation and polymerization
Correlations between plasma variables and the deposition process of Si films from chlorosilanes in low pressure RF plasma of argon and hydrogen
The dissociation of chlorosilanes to silicon and its deposition on a solid substrate in a RF plasma of mixtures of argon and hydrogen were investigated as a function of the macrovariables of the plasma. The dissociation mechanism of chlorosilanes and HCl as well as the formation of Si in the plasma state were studied by sampling the plasma with a quadrupole mass spectrometer. Macrovariables such as pressure, net RF power input and locations in the plasma reactor strongly influence the kinetics of dissociation. The deposition process of microcrystalline silicon films and its chlorine contamination were correlated to the dissociation mechanism of chlorosilanes and HCl
Similarity classes of 3x3 matrices over a local principal ideal ring
In this paper similarity classes of three by three matrices over a local
principal ideal commutative ring are analyzed. When the residue field is
finite, a generating function for the number of similarity classes for all
finite quotients of the ring is computed explicitly.Comment: 14 pages, final version, to appear in Communications in Algebr
Analysis of in Vivo Plant Stem Impedance Variations in Relation with External Conditions Daily Cycle
World population growth and desertification are the most severe issue to agricultural food production. Smart agriculture is a promising solution to ensure food security. The use of sensors to monitor crop production can help farmers improve the yield and reduce water consumption. Here we propose a study where the electrical impedance of green plants' stem is analyzed in vivo, along with environmental conditions. In particular, the variations associated with the daily cycle are highlighted. These analyses lead to the possibility of understanding plant status directly from stem impedance
A photometric redshift of for the \agile GRB 080514B
Aims: The AGILE gamma-ray burst GRB 080514B is the first burst with detected
emission above 30 MeV and an optical afterglow. However, no spectroscopic
redshift for this burst is known.
Methods: We compiled ground-based photometric optical/NIR and millimeter data
from several observatories, including the multi-channel imager GROND, as well
as ultraviolet \swift UVOT and X-ray XRT observations. The spectral energy
distribution of the optical/NIR afterglow shows a sharp drop in the \swift UVOT
UV filters that can be utilized for the estimation of a redshift.
Results: Fitting the SED from the \swift UVOT band to the band, we
estimate a photometric redshift of , consistent with the
pseudo redshift reported by Pelangeon & Atteia (2008) based on the gamma-ray
data.
Conclusions: The afterglow properties of GRB 080514B do not differ from those
exhibited by the global sample of long bursts, supporting the view that
afterglow properties are basically independent of prompt emission properties.Comment: submitted to A&A letter
The Sedentary Multi-Frequency Survey. I. Statistical Identification and Cosmological Properties of HBL BL Lacs
We have assembled a multi-frequency database by cross-correlating the NVSS
catalog of radio sources with the RASSBSC list of soft X-ray sources, obtaining
optical magnitude estimates from the Palomar and UK Schmidt surveys as provided
by the APM and COSMOS on-line services. By exploiting the nearly unique
broad-band properties of High-Energy Peaked (HBL) BL Lacs we have statistically
identified a sample of 218 objects that is expected to include about 85% of BL
Lacs and that is therefore several times larger than all other published
samples of HBLs. Using a subset (155 objects) that is radio flux limited and
statistically well-defined we have derived the \vovm distribution and the
LogN-LogS of extreme HBLs (fx/fr >= 3E-10 erg/cm2/s/Jansky) down to 3.5 mJy. We
find that the LogN-LogS flattens around 20 mJy and that = 0.42 +/- 0.02.
This extends to the radio band earlier results, based on much smaller X-ray
selected samples, about the anomalous cosmological observational properties of
HBL BL Lacs. A comparison with the expected radio LogN-LogS of all BL Lacs
(based on a beaming model) shows that extreme HBLs make up roughly 2% of the BL
Lac population, independently of radio flux. This result, together with the
flatness of the radio logN-logS at low fluxes, is in contrast with the
predictions of a recent model which assumes an anti-correlation between peak
frequency and bolometric luminosity. The extreme fx/fr flux ratios and high
X-ray fluxes of these BL Lacs makes them good candidate TeV sources, some of
the brighter (and closer) ones possibly detectable with the current generation
of Cerenkov telescopes.Comment: 11 pages, LaTeX, 6 ps figures. Accepted for publication in MNRA
Infinite-Duration Poorman-Bidding Games
In two-player games on graphs, the players move a token through a graph to produce an infinite path, which determines the winner or payoff of the game. Such games are central in formal verification since they model the interaction between a non-terminating system and its environment. We study bidding games in which the players bid for the right to move the token. Two bidding rules have been defined. In Richman bidding, in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Poorman bidding is similar except that the winner of the bidding pays the “bank” rather than the other player. While poorman reachability games have been studied before, we present, for the first time, results on infinite-duration poorman games. A central quantity in these games is the ratio between the two players’ initial budgets. The questions we study concern a necessary and sufficient ratio with which a player can achieve a goal. For reachability objectives, such threshold ratios are known to exist for both bidding rules. We show that the properties of poorman reachability games extend to complex qualitative objectives such as parity, similarly to the Richman case. Our most interesting results concern quantitative poorman games, namely poorman mean-payoff games, where we construct optimal strategies depending on the initial ratio, by showing a connection with random-turn based games. The connection in itself is interesting, because it does not hold for reachability poorman games. We also solve the complexity problems that arise in poorman bidding games
Congenital tumors: imaging when life just begins
BACKGROUND: The technical developments of imaging methods over the last 2 decades are changing our knowledge of perinatal oncology. Fetal ultrasound is usually the first imaging method used and thus constitutes the reference prenatal study, but MRI seems to be an excellent complementary method for evaluating the fetus. The widespread use of both techniques has increased the diagnosis rates of congenital tumors. During pregnancy and after birth, an accurate knowledge of the possibilities and limits of the different imaging techniques available would improve the information obtainable, thus helping the medical team to make the most appropriate decisions about therapy and to inform the family about the prognosis.
CONCLUSION: In this review article, we describe the main congenital neoplasms, their prognosis and their imaging characteristics with the different pre- and postnatal imaging methods available
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