1,303 research outputs found
Invariants for Lagrangian tori
We define an simple invariant of an embedded nullhomologous Lagrangian torus
and use this invariant to show that many symplectic 4-manifolds have infinitely
many pairwise symplectically inequivalent nullhomologous Lagrangian tori. We
further show that for a large class of examples that lambda(T) is actually a
C-infinity invariant. In addition, this invariant is used to show that many
symplectic 4-manifolds have nontrivial homology classes which are represented
by infinitely many pairwise inequivalent Lagrangian tori, a result first proved
by S Vidussi for the homotopy K3-surface obtained from knot surgery using the
trefoil knot in [Lagrangian surfaces in a fixed homology class: existence of
knotted Lagrangian tori, J. Diff. Geom. (to appear)].Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol8/paper25.abs.htm
Prospects for high-resolution microwave spectroscopy of methanol in a Stark-deflected molecular beam
Recently, the extremely sensitive torsion-rotation transitions in methanol
have been used to set a tight constraint on a possible variation of the
proton-to-electron mass ratio over cosmological time scales. In order to
improve this constraint, laboratory data of increased accuracy will be
required. Here, we explore the possibility for performing high-resolution
spectroscopy on methanol in a Stark-deflected molecular beam. We have
calculated the Stark shift of the lower rotational levels in the ground
torsion-vibrational state of CH3OH and CD3OH molecules, and have used this to
simulate trajectories through a typical molecular beam resonance setup.
Furthermore, we have determined the efficiency of non-resonant multi-photon
ionization of methanol molecules using a femtosecond laser pulse. The described
setup is in principle suited to measure microwave transitions in CH3OH at an
accuracy below 10^{-8}
Electron Removal From Molecular Hydrogen By Fully Stripped Ions At Intermediate Energies
A classical phase-space model of the hydrogen molecule is presented and applied to the study of the electron-capture and -ionization processes in collisions of fully stripped ions with H2 at intermediate impact energies and charge states from 1 to 10. The model is based on the independent-electron and the impact-parameter approximations. The electron impinging-ion and electron target-nuclei interactions are exactly taken into account. The interaction between the electrons is approximated by model potentials. The calculated total cross sections for production of free electrons and capture of one electron are in good agreement with different experimental data. The ratio between the capture cross sections from molecular and atomic hydrogen targets is also analyzed and compared with available empirical scaling\u27s. It is found that this ratio varies from a value less than 1 at low impact energy to 4 at higher energies. The reasons for these differences are discussed. A comparison is made between the capture cross sections for different orientations of the hydrogen molecule. © 1989 The American Physical Society
Subshell Electron Capture In Collisions Of Fully Stripped Ions With He And H2 At Intermediate Energies
Classical phase-space models of the hydrogen molecule and helium are utilized to study shell and subshell electron-capture processes in collisions of fully stripped ions on charge states from 1 to 15 with H2 and He at intermediate impact energies (20200 keV/amu). Autoionization after double electron capture is approximated and is found to be an important channel for high projectile charges. The resulting (n,l) distributions for proton impact of He and H2 as well as total capture cross sections are found to be in very good agreement with experimental data. l distributions for high projectile charges are also analyzed for n levels for which autoionization is negligible. It is found that electrons are captured preferentially to large l values. © 1990 The American Physical Society
Classical Description And Calculation Of Ionization In Collisions Of 100 Ev Electrons And Positrons With He And H2
In order to explore the range of applicability of the classical trajectory Monte Carlo technique concerning the phenomena associated with light-particle impact of atoms and molecules we present calculations of the singly and doubly differential cross sections for 100 eV electron and positron impact of He and H2 Through comparison with experimental measurements it is noted in what regimes of ejection energy and angle the classical model describes reasonably the process of ionization by electrons. We find that reasonable agreement is obtained regarding the integrated (singly differential and total) cross sections while the features of the doubly differential cross section which evidently come about due to quantum mechanical aspects of the collision are not reproduced. In these instances the classical cross sections reflect an averaging over electron angles and energies of the observed doubly differential cross sections. Difficulties associated with the classical model of the many electron atom which arise specifically in light-particle impact are discussed as well as a comparison with a distorted wave Born approximation for electron impact of helium. © 1992 IOP Publication Ltd
Identification of an l-Arabitol Transporter from Aspergillus niger
l-arabitol is an intermediate of the pentose catabolic pathway in fungi but can also be used as a carbon source by many fungi, suggesting the presence of transporters for this polyol. In this study, an l-arabitol transporter, LatA, was identified in Aspergillus niger. Growth and expression profiles as well as sugar consumption analysis indicated that LatA only imports l-arabitol and is regulated by the arabinanolytic transcriptional activator AraR. Moreover, l-arabitol production from wheat bran was increased in a metabolically engineered A. niger mutant by the deletion of latA, indicating its potential for improving l-arabitol-producing cell factories. Phylogenetic analysis showed that homologs of LatA are widely conserved in fungi
Measurement of the Wear Properties of Metallic Solids with a Falex Lubricant Testing Machine
A modified Falex Lubricant Testing Machine has been used to determine wear properties of metallic solids. In particular, wear mass loss, wear volume loss, wear rates, and other parameters have been determined for a basic steel, as heat treated and after ion implantation. Wear rate improvements of more than an order of magnitude were found in a nickel-chrome steel (SAE 3135) implanted with 2.5x1017 N+2/cm2. Wear tests were conducted with a cylinder-in-groove geometry in a mild lubricating oil with loads greater than 540 N, which corresponded to pressures which exceeded 108N/m2. A detailed analysis of the data is presented
Light Field Saliency Detection with Deep Convolutional Networks
Light field imaging presents an attractive alternative to RGB imaging because
of the recording of the direction of the incoming light. The detection of
salient regions in a light field image benefits from the additional modeling of
angular patterns. For RGB imaging, methods using CNNs have achieved excellent
results on a range of tasks, including saliency detection. However, it is not
trivial to use CNN-based methods for saliency detection on light field images
because these methods are not specifically designed for processing light field
inputs. In addition, current light field datasets are not sufficiently large to
train CNNs. To overcome these issues, we present a new Lytro Illum dataset,
which contains 640 light fields and their corresponding ground-truth saliency
maps. Compared to current light field saliency datasets [1], [2], our new
dataset is larger, of higher quality, contains more variation and more types of
light field inputs. This makes our dataset suitable for training deeper
networks and benchmarking. Furthermore, we propose a novel end-to-end CNN-based
framework for light field saliency detection. Specifically, we propose three
novel MAC (Model Angular Changes) blocks to process light field micro-lens
images. We systematically study the impact of different architecture variants
and compare light field saliency with regular 2D saliency. Our extensive
comparisons indicate that our novel network significantly outperforms
state-of-the-art methods on the proposed dataset and has desired generalization
abilities on other existing datasets.Comment: 14 pages, 14 figure
Union Impacts on the Receipt of Workers' Compensation Benefits
La convention collective et lâobligation dâaccommodement selon lâarrĂȘt Okanaga
Feqâș+ H, H2and He Electron Loss And He2++ H(N = 1, 2) Electron Capture Cross Sections: Processes Of Interest In Fusion Plasmas
Cross sections have been calculated utilizing the classical trajectory Monte Carlo method for collisional processes of special interest to plasma fusion research. Specifically, H1H2and He total electron loss cross sections for the impact by Feq+(1 \u3c q \u3c 26) impurity ions, in the energy range of 50 to 500keV/u, are presented. These results illustrate a clear departure for low charge states (q \u3c 10) from scaling of the cross section with projectile charge (q). Further, cross sections for electron capture from both the ground and n = 2 states of H by 30 to lOOkeV/u He2+impact are tabulated as function of final n-level, yielding information for neutral beam heating models. © 1991 IOP Publishing Ltd
- âŠ