327 research outputs found
Helium in superstrong magnetic fields
We investigate the helium atom embedded in a superstrong magnetic field
gamma=100-10000 au. All effects due to the finite nuclear mass for vanishing
pseudomomentum are taken into account. The influence and the magnitude of the
different finite mass effects are analyzed and discussed. Within our full
configuration interaction approach calculations are performed for the magnetic
quantum numbers M=0,-1,-2,-3, singlet and triplet states, as well as positive
and negative z parities. Up to six excited states for each symmetry are
studied. With increasing field strength the number of bound states decreases
rapidly and we remain with a comparatively small number of bound states for
gamma=10^4 au within the symmetries investigated here.Comment: 16 pages, including 14 eps figures, submitted to Phys. Rev.
Beam Loss Control for the Unstripped Ions from the PS2 Charge Exchange Injection
Control of beam losses is an important aspect of the H-injection system for the PS2, a proposed replacement of the CPS in the CERN injector complex. H- ions may pass the foil unstripped or be partially stripped to excited H0 states which may be stripped in the subsequent strong-field chicane magnet. Depending on the choice of the magnetic field, atoms in the ground and first excited states can be extracted and dumped. The conceptual design of the waste beam handling is presented, including local collimation and the dump line, both of which must take into account the divergence of the beam from stripping in fringe fields. Beam load estimates and activation related requirements of the local collimators and dump are briefly discussed
Hydrogen atom moving across a strong magnetic field: analytical approximations
Analytical approximations are constructed for binding energies,
quantum-mechanical sizes and oscillator strengths of main radiative transitions
of hydrogen atoms arbitrarily moving in magnetic fields 10^{12}-10^{13} G.
Examples of using the obtained approximations for determination of maximum
transverse velocity of an atom and for evaluation of absorption spectra in
magnetic neutron star atmospheres are presented.Comment: 17 pages, 3 figures, 5 tables, LaTeX with IOP style files (included).
In v.2, Fig.1 and Table 5 have been corrected. In v.3, a misprint in the fit
for oscillator strengths, Eq.(21), has been correcte
The helium atom in a strong magnetic field
We investigate the electronic structure of the helium atom in a magnetic
field b etween B=0 and B=100a.u. The atom is treated as a nonrelativistic
system with two interactin g electrons and a fixed nucleus. Scaling laws are
provided connecting the fixed-nucleus Hamiltonia n to the one for the case of
finite nuclear mass. Respecting the symmetries of the electronic Ham iltonian
in the presence of a magnetic field, we represent this Hamiltonian as a matrix
with res pect to a two-particle basis composed of one-particle states of a
Gaussian basis set. The corresponding generalized eigenvalue problem is solved
numerically, providing in the present paper results for vanish ing magnetic
quantum number M=0 and even or odd z-parity, each for both singlet and triplet
spin symmetry. Total electronic energies of the ground state and the first few
excitations in each su bspace as well as their one-electron ionization energies
are presented as a function of the magnetic fie ld, and their behaviour is
discussed. Energy values for electromagnetic transitions within the M=0 sub
space are shown, and a complete table of wavelengths at all the detected
stationary points with respect to their field dependence is given, thereby
providing a basis for a comparison with observed ab sorption spectra of
magnetic white dwarfs.Comment: 21 pages, 4 Figures, acc.f.publ.in J.Phys.
Spectrum of Neutral Helium in Strong Magnetic Fields
We present extensive and accurate calculations for the excited state spectrum
of spin-polarized neutral helium in a range of magnetic field strengths up to
G. Of considerable interest to models of magnetic white dwarf stellar
atmospheres, we also present results for the dipole strengths of the low lying
transitions among these states. Our methods rely on a systematically saturated
basis set approach to solving the Hartree--Fock self-consistent field
equations, combined with an ``exact'' stochastic method to estimate the
residual basis set truncation error and electron correlation effects. We also
discuss the applicability of the adiabatic approximation to strongly magnetized
multi-electron atoms.Comment: 19 pages, 7 figures, 10 table
In vitro culture of Plasmodium berghei-ANKA maintains infectivity of mouse erythrocytes inducing cerebral malaria
<p>Abstract</p> <p>Background</p> <p>Infection with <it>Plasmodium berghei </it>is a widely used model of murine malaria and a powerful tool for reverse genetic and pathogenesis studies. However, the efficacy of <it>in vitro </it>reinvasion of erythrocytes is generally low, limiting <it>in vitro </it>studies.</p> <p>Methods</p> <p><it>Plasmodium berghei </it>ANKA-infected blood obtained from a susceptible infected mouse was cultured in various conditions and <it>in vitro </it>parasitaemia was measured every day to evaluate the rate of reinvasion.</p> <p>Results</p> <p>High quality culture media were used and reinvasion rates were improved by vigorous orbital shaking of the flask and increasing density of the medium with gelatin.</p> <p>Discussion</p> <p>Using these settings, reinvasion of normal mouse erythrocytes by the parasite was obtained <it>in vitro </it>over two weeks with preservation of the infectivity <it>in vivo</it>.</p
Electromagnetic transitions of the helium atom in superstrong magnetic fields
We investigate the electromagnetic transition probabilities for the helium
atom embedded in a superstrong magnetic field taking into account the finite
nuclear mass. We address the regime \gamma=100-10000 a.u. studying several
excited states for each symmetry, i.e. for the magnetic quantum numbers
0,-1,-2,-3, positive and negative z parity and singlet and triplet symmetry.
The oscillator strengths as a function of the magnetic field, and in particular
the influence of the finite nuclear mass on the oscillator strengths are shown
and analyzed.Comment: 10 pages, 8 figure
Isotope shift in the electron affinity of chlorine
The specific mass shift in the electron affinity between ^{35}Cl and ^{37}Cl
has been determined by tunable laser photodetachment spectroscopy to be
-0.51(14) GHz. The isotope shift was observed as a difference in the onset of
the photodetachment process for the two isotopes. In addition, the electron
affinity of Cl was found to be 29138.59(22) cm^{-1}, giving a factor of 2
improvement in the accuracy over earlier measurements. Many-body calculations
including lowest-order correlation effects demonstrates the sensitivity of the
specific mass shift and show that the inclusion of higher-order correlation
effects would be necessary for a quantitative description.Comment: 16 pages, 6 figures, LaTeX2e, amsmat
High-throughput amplicon sequencing reveals distinct communities within a corroding concrete sewer system
This study investigated the variation in microbially induced concrete corrosion communities at different circumferential locations of a real sewer pipe and the effects of a wastewater flooding event on the community. Three distinct microbial community groups were found in different corrosion samples. The physico-chemical properties of the corrosion layers and the microbial communities were distinct for the cross-sectional positions within the pipe, ie ceiling, wall and tidal zones. The microbial communities detected from the same positions in the pipe were consistent over the length of the pipe, as well as being consistent between the replicate pipes. The dominating ceiling communities were members of the bacterial orders Rhodospirillales, Acidithiobacillales, Actinomycetales, Xanthomonadales and Acidobacteriales. The wall communities were composed of members of the Xanthomonadales, Hydrogenophilales, Chromatiales and Sphingobacteriales. The tidal zones were dominated by eight bacterial and one archaeal order, with the common physiological trait of anaerobic metabolism. Sewage flooding within the sewer system did not change the tidal and wall communities, although the corrosion communities in ceiling samples were notably different, becoming more similar to the wall and tidal samples. This suggests that sewage flooding has a significant impact on the corrosion community in sewers
The ground state of the carbon atom in strong magnetic fields
The ground and a few excited states of the carbon atom in external uniform
magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for
field strengths ranging from zero up to 2.35 10^9 T. With increasing field
strength the ground state undergoes six transitions involving seven different
electronic configurations which belong to three groups with different spin
projections S_z=-1,-2,-3. For weak fields the ground state configuration arises
from the field-free 1s^2 2s^2 2p_0 2p_{-1}, S_z=-1 configuration. With
increasing field strength the ground state involves the four S_z=-2
configurations 1s^22s2p_0 2p_{-1}2p_{+1}, 1s^22s2p_0 2p_{-1}3d_{-2}, 1s^22p_0
2p_{-1}3d_{-2}4f_{-3} and 1s^22p_{-1}3d_{-2}4f_{-3}5g_{-4}, followed by the two
fully spin polarized S_z=-3 configurations 1s2p_02p_{-1}3d_{-2}4f_{-3}5g_{-4}
and 1s2p_{-1}3d_{-2}4f_{-3}5g_{-4}6h_{-5}. The last configuration forms the
ground state of the carbon atom in the high field regime \gamma>18.664. The
above series of ground state configurations is extracted from the results of
numerical calculations for more than twenty electronic configurations selected
due to some general energetical arguments.Comment: 6 figures,acc. Phys.Rev.
- âŠ