1,010 research outputs found
Slip avalanches in crystal plasticity: scaling of the avalanche cutoff
Plastic deformation of crystals proceeds through a sequence of intermittent
slip avalanches with scale-free (power-law) size distribution. On macroscopic
scales, however, plastic flow is known to be smooth and homogeneous. In the
present letter we use a recently proposed continuum model of slip avalanches to
systematically investigate the nature of the cut-off which truncates scale-free
behavior at large avalanche sizes. The dependence of the cut-off on system
size, geometry, and driving mode, but also on intrinsic parameters such as the
strain hardening rate is established. Implications for the observability of
avalanche behavior in microscopic and macroscopic samples are discussed.Comment: 12 pages, 4 figure
Enhanced Sensitivity to the Time Variation of the Fine-Structure Constant and in Diatomic Molecules: A Closer Examination of Silicon Monobromide
Recently it was pointed out that transition frequencies in certain diatomic
molecules have an enhanced sensitivity to variations in the fine-structure
constant and the proton-to-electron mass ratio due to a near
cancellation between the fine-structure and vibrational interval in a ground
electronic multiplet [V.~V.~Flambaum and M.~G.~Kozlov, Phys. Rev. Lett.~{\bf
99}, 150801 (2007)]. One such molecule possessing this favorable quality is
silicon monobromide. Here we take a closer examination of SiBr as a candidate
for detecting variations in and . We analyze the rovibronic
spectrum by employing the most accurate experimental data available in the
literature and perform \emph{ab initio} calculations to determine the precise
dependence of the spectrum on variations in . Furthermore, we calculate
the natural linewidths of the rovibronic levels, which place a fundamental
limit on the accuracy to which variations may be determined.Comment: 8 pages, 2 figure
Homogeneous Gold Catalysis through Relativistic Effects: Addition of Water to Propyne
In the catalytic addition of water to propyne the Au(III) catalyst is not
stable under non-relativistic conditions and dissociates into a Au(I) compound
and Cl2. This implies that one link in the chain of events in the catalytic
cycle is broken and relativity may well be seen as the reason why Au(III)
compounds are effective catalysts.Comment: 12 pages, 3 figures, 1 tabl
Identification of the slow E3 transition 136mCs -> 136Cs with conversion electrons
We performed at ISOLDE the spectroscopy of the decay of the 8- isomer in
136Cs by and conversion-electron detection. For the first time the excitation
energy of the isomer and the multipolarity of its decay have been measured. The
half-life of the isomeric state was remeasured to T1/2 = 17.5(2) s. This isomer
decays via a very slow 518 keV E3 transition to the ground state. In addition
to this, a much weaker decay branch via a 413 keV M4 and a subsequent 105 keV
E2 transition has been found. Thus we have found a new level at 105 keV with
spin 4+ between the isomeric and the ground state. The results are discussed in
comparison to shell model calculations.Comment: Phys. Rev. C accepted for publicatio
Risk factors for allogeneic stem cell transplantation in patients with myelofibrosis with myeloid metaplasia
Cohesive energies of cubic III-V semiconductors
Cohesive energies for twelve cubic III-V semiconductors with zincblende
structure have been determined using an ab-initio scheme. Correlation
contributions, in particular, have been evaluated using the coupled-cluster
approach with single and double excitations (CCSD). This was done by means of
increments obtained for localized bond orbitals and for pairs and triples of
such bonds. Combining these results with corresponding Hartree-Fock data, we
recover about 92 \% of the experimental cohesive energies.Comment: 16 pages, 1 figure, late
First identification of large electric monopole strength in well-deformed rare earth nuclei
Excited states in the well-deformed rare earth isotopes Sm and
Er were populated via ``safe'' Coulomb excitation at the Munich MLL
Tandem accelerator. Conversion electrons were registered in a cooled Si(Li)
detector in conjunction with a magnetic transport and filter system, the
Mini-Orange spectrometer. For the first excited state in Sm at
1099 keV a large value of the monopole strength for the transition to the
ground state of could be extracted. This confirms the interpretation of the lowest
excited state in Sm as the collective -vibrational
excitation of the ground state. In Er the measured large electric
monopole strength of clearly identifies the state at 1934 keV to be the
-vibrational excitation of the ground state.Comment: submitted to Physics Letters
Calculation of the positron bound state with the copper atom
A new relativistic method for calculation of positron binding to atoms is
presented. The method combines a configuration interaction treatment of the
valence electron and the positron with a many-body perturbation theory
description of their interaction with the atomic core. We apply this method to
positron binding by the copper atom and obtain the binding energy of 170 meV (+
- 10%). To check the accuracy of the method we use a similar approach to
calculate the negative copper ion. The calculated electron affinity is 1.218
eV, in good agreement with the experimental value of 1.236 eV. The problem of
convergence of positron-atom bound state calculations is investigated, and
means to improve it are discussed. The relativistic character of the method and
its satisfactory convergence make it a suitable tool for heavier atoms.Comment: 15 pages, 5 figures, RevTe
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