4,961 research outputs found
Large area radio frequency plasma for microelectronics processing
Includes bibliographical references (page 874).Radio-frequency (rf) inductively coupled planar plasma (ICP) provides a better way to generate spatially confined high density gas discharge plasmas for microelectronics processing. Commercial processing equipment using this technique is currently available, but is limited in size to 20 cm in diameter by problems with plasma uniformity and antenna dielectric window erosion. We have developed a new planar ICP antenna and dielectric window design that allows for larger dimensions (up to 50 cm in diameter) with good uniformity. The current art ICP antenna requires a thick quartz (or ceramic) plate vacuum window to separate the rf inductor and the plasma. The larger the antenna diameter the thicker the dielectric. The thick dielectric reduces inductive coupling efficiency. The large area coil and associated matching network can introduce plasma uniformity problems. Our device incorporates both the rf inductor and the dielectric window inside the vacuum chamber, allowing space for a thin layer of quartz or other dielectric material. Thus, the dielectric window design is only focused on materials for the given process chemistry to be placed between the coil and the excited plasma, rather than also including mechanical strength to hold a vacuum over a wide area. This thin dielectric layer with our newly designed planar coil coupler allows the plasma to be scaled to a 50 cm diameter while maintaining radial uniformity. In this article we report only plasma ashing results for a 20 cm planar ICP device that shows 2% nonuniformity across 15 cm wafers. The measured flux of atomic oxygen and atomic hydrogen generated by a larger planar ICP scale device is also presented
Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry
Within the “Compartmentalised Smart Factory” approach of the ONE-FLOW project the implementation of different catalysts in “compartments” provided by Pickering emulsions and their application in continuous flow is targeted. We present here the development of heterogeneous Pd-catalysts that are ready to be used in combination with biocatalysts for catalytic cascade syntheses of active pharmaceutical ingredients (APIs). In particular, we focus on the application of the catalytic systems for Suzuki-Miyaura cross coupling reactions, which is the key step in the syntheses of the targeted APIs valsartan and sacubitril. An immobilised enzyme will accomplish the final product formation via hydrolysis. In order to create large interfacial area for the catalytic reactions and to keep the reagents separated until required, the catalyst particles are used to stabilise Pickering emulsions of oil and water. A set of Ce-Sn-Pd-oxides with the molecular formula Ce0.99-xSnxPd0.01O2-(x= 0-0.99) has been prepared utilising a simple single-step solution combustion method. The high applicability of the catalysts for different functional groups and their minimal leaching behaviour is demonstrated with various Suzuki-Miyaura cross coupling reactions in batch as well as in continuous flow employing the so-called “Plug & Play reactor”. Finally, we demonstrate the use of these particles as the sole emulsifier of oil + water emulsions for a range of oils
Magnetic and superconducting instabilities of the Hubbard model at the van Hove filling
We use a novel temperature-flow renormalization group technique to analyze
magnetic and superconducting instabilities in the two-dimensional t-t' Hubbard
model for particle densities close to the van Hove filling as a function of the
next-nearest neighbor hopping t'. In the one-loop flow at the van Hove filling,
the characteristic temperature for the flow to strong coupling is suppressed
drastically around t'_c approx. -0.33t, suggesting a quantum critical point
between d-wave pairing at moderate t'>t'_c and ferromagnetism for t'<t'_c. Upon
increasing the particle density in the latter regime the leading instability
occurs in the triplet pairing channel.Comment: 4 pages, to appear in Physical Review Letter
A subarcsecond near-infrared view of massive galaxies at z > 1 with Gemini Multiconjugate Adaptive Optics
We present images taken using the Gemini South Adaptive Optics Imager (GSAOI)
with the Gemini Multiconjugate Adaptive Optics System (GeMS) in three 2
arcmin fields in the Spitzer Extragalactic Representative Volume Survey.
These GeMS/GSAOI observations are among the first resolution
data in the near-infrared spanning extragalactic fields exceeding
in size. We use these data to estimate galaxy sizes, obtaining
results similar to those from studies with the Hubble Space Telescope, though
we find a higher fraction of compact star forming galaxies at . To
disentangle the star-forming galaxies from active galactic nuclei (AGN), we use
multiwavelength data from surveys in the optical and infrared, including
far-infrared data from Herschel, as well as new radio continuum data from the
Australia Telescope Compact Array and Very Large Array. We identify
ultraluminous infrared galaxies (ULIRGs) at , which consist of a
combination of pure starburst galaxies and Active Galactic Nuclei
(AGN)/starburst composites. The ULIRGs show signs of recent merger activity,
such as highly disturbed morphologies and include a rare candidate triple AGN.
We find that AGN tend to reside in hosts with smaller scale sizes than purely
star-forming galaxies of similar infrared luminosity. Our observations
demonstrate the potential for MCAO to complement the deeper galaxy surveys to
be made with the James Webb Space Telescope.Comment: 20 pages, AJ, in pres
Exact Histogram Specification Optimized for Structural Similarity
An exact histogram specification (EHS) method modifies its input image to
have a specified histogram. Applications of EHS include image (contrast)
enhancement (e.g., by histogram equalization) and histogram watermarking.
Performing EHS on an image, however, reduces its visual quality. Starting from
the output of a generic EHS method, we maximize the structural similarity index
(SSIM) between the original image (before EHS) and the result of EHS
iteratively. Essential in this process is the computationally simple and
accurate formula we derive for SSIM gradient. As it is based on gradient
ascent, the proposed EHS always converges. Experimental results confirm that
while obtaining the histogram exactly as specified, the proposed method
invariably outperforms the existing methods in terms of visual quality of the
result. The computational complexity of the proposed method is shown to be of
the same order as that of the existing methods.
Index terms: histogram modification, histogram equalization, optimization for
perceptual visual quality, structural similarity gradient ascent, histogram
watermarking, contrast enhancement
On the algebraic invariant curves of plane polynomial differential systems
We consider a plane polynomial vector field of degree
. To each algebraic invariant curve of such a field we associate a compact
Riemann surface with the meromorphic differential . The
asymptotic estimate of the degree of an arbitrary algebraic invariant curve is
found. In the smooth case this estimate was already found by D. Cerveau and A.
Lins Neto [Ann. Inst. Fourier Grenoble 41, 883-903] in a different way.Comment: 10 pages, Latex, to appear in J.Phys.A:Math.Ge
The TRENDS High-Contrast Imaging Survey. VII. Discovery of a Nearby Sirius-like White Dwarf System (HD 169889)
Monitoring the long-term radial velocity (RV) and acceleration of nearby
stars has proven an effective method for directly detecting binary and
substellar companions. Some fraction of nearby RV trend systems are expected to
be comprised of compact objects that likewise induce a systemic Doppler signal.
In this paper, we report the discovery of a white dwarf companion found to
orbit the nearby ( mas) G9 V star HD 169889.
High-contrast imaging observations using NIRC2 at Keck and LMIRCam at the LBT
uncover the (, ) companion
at an angular separation of 0.8'' (28 au). Thirteen years of precise Doppler
observations reveal a steep linear acceleration in RV time series and place a
dynamical constraint on the companion mass of . This "Sirius-like" system adds to the census of white dwarf
companions suspected to be missing in the solar neighborhood.Comment: Accepted to Ap
From M-ary Query to Bit Query: a new strategy for efficient large-scale RFID identification
The tag collision avoidance has been viewed as one of the most important research problems in RFID communications and bit tracking technology has been widely embedded in query tree (QT) based algorithms to tackle such challenge. Existing solutions show further opportunity to greatly improve the reading performance because collision queries and empty queries are not fully explored. In this paper, a bit query (BQ) strategy based Mary query tree protocol (BQMT) is presented, which can not only eliminate idle queries but also separate collided tags into many small subsets and make full use of the collided bits. To further optimize the reading performance, a modified dual prefixes matching (MDPM) mechanism is presented to allow multiple tags to respond in the same slot and thus significantly reduce the number of queries. Theoretical analysis and simulations are supplemented to validate the effectiveness of the proposed BQMT and MDPM, which outperform the existing QT-based algorithms. Also, the BQMT and MDPM can be combined to BQMDPM to improve the reading performance in system efficiency, total identification time, communication complexity and average energy cost
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