180,445 research outputs found
Pyrite oxidation under initially neutral pH conditions and in the presence of Acidithiobacillus ferrooxidans and micromolar hydrogen peroxide
Hydrogen peroxide (H2O2) at a micromolar level played a role in the microbial surface oxidation of pyrite crystals under initially neutral pH. When the mineral-bacteria system
was cyclically exposed to 50 μM H2O2, the colonization of Acidithiobacillus ferrooxidans onto the mineral surface was markedly enhanced, as compared to the control(no added H2O2). This can be attributed to the effects of H2O2 on increasing the roughness of the mineral surfaces, as well as the acidity and Fe2+ concentration at the mineral-solution interfaces. All of these effects tended to create more favourable nanoto micro-scale environments in the mineral surfaces for the cell adsorption. However, higher H2O2 levels inhibited the attachment of cells onto the mineral surfaces, possibly due to the oxidative stress in the bacteria when they approached the mineral surfaces
where high levels of free radicals are present as a result of Fenton-like reactions. The more aggressive nature of H2O2 as an oxidant caused marked surface flaking of the
mineral surface. The XPS results suggest that H2O2 accelerated the oxidation of pyrite-S and consequently facilitated the overall corrosion cycle of pyrite surfaces. This was accompanied by pH drop in the solution in contact with the pyrite cubes
Minimal Permutations and 2-Regular Skew Tableaux
Bouvel and Pergola introduced the notion of minimal permutations in the study
of the whole genome duplication-random loss model for genome rearrangements.
Let denote the set of minimal permutations of length
with descents, and let . They derived that
and , where is the -th
Catalan number. Mansour and Yan proved that . In
this paper, we consider the problem of counting minimal permutations in
with a prescribed set of ascents. We show that such
structures are in one-to-one correspondence with a class of skew Young
tableaux, which we call -regular skew tableaux. Using the determinantal
formula for the number of skew Young tableaux of a given shape, we find an
explicit formula for . Furthermore, by using the Knuth equivalence,
we give a combinatorial interpretation of a formula for a refinement of the
number .Comment: 19 page
Quantum sensing of rotation velocity based on transverse field Ising model
We study a transverse-field Ising model (TFIM) in a rotational reference
frame. We find that the effective Hamiltonian of the TFIM of this system
depends on the system's rotation velocity. Since the rotation contributes an
additional transverse field, the dynamics of TFIM sensitively responses to the
rotation velocity at the critical point of quantum phase transition. This
observation means that the TFIM can be used for quantum sensing of rotation
velocity that can sensitively detect rotation velocity of the total system at
the critical point. It is found that the resolution of the quantum sensing
scheme we proposed is characterized by the half-width of Loschmidt echo of the
dynamics of TFIM when it couples to a quantum system S. And the resolution of
this quantum sensing scheme is proportional to the coupling strength \delta
between the quantum system S and the TFIM, and to the square root of the number
of spins N belonging the TFIM.Comment: 6 pages,6 figure
Crystal growth and in-plane optical properties of TlBaCaCuO (n=1,2,3) superconductors
Single crystals of thallium-based cuprates with the general formula
TlBaCaCuO(n=1,2,3) have been grown by the flux
method. The superconducting transition temperatures determined by the ac
magnetic susceptibility are 92 K, 109 K, and 119 K for n=1,2,3 respectively.
X-ray diffraction measurements and EDX compositional analysis were described.
We measured in-plane optical reflectance from room temperature down to 10 K,
placing emphasis on Tl-2223. The reflectance roughly has a linear-frequency
dependence above superconducting transition temperature, but displays a
pronounced knee structure together with a dip-like feature at higher frequency
below T. Correspondingly, the ratio of the reflectances below and above
T displays a maximum and a minimum near those feature frequencies. In
particular, those features in Tl2223 appear at higher energy scale than Tl2212,
and Tl2201. The optical data are analyzed in terms of spectral function. We
discussed the physical consequences of the data in terms of both clean and
dirty limit.Comment: 8 pages, 13 figures, to be published in Phys. Rev.
Scaling of Anisotropic Flows and Nuclear Equation of State in Intermediate Energy Heavy Ion Collisions
Elliptic flow () and hexadecupole flow () of light clusters have
been studied in details for 25 MeV/nucleon Kr + Sn at large
impact parameters by Quantum Molecular Dynamics model with different potential
parameters. Four parameter sets which include soft or hard equation of state
(EOS) with/without symmetry energy term are used. Both number-of-nucleon ()
scaling of the elliptic flow versus transverse momentum () and the scaling
of versus have been demonstrated for the light clusters
in all above calculation conditions. It was also found that the ratio of
keeps a constant of 1/2 which is independent of for all the
light fragments. By comparisons among different combinations of EOS and
symmetry potential term, the results show that the above scaling behaviors are
solid which do not depend the details of potential, while the strength of flows
is sensitive to EOS and symmetry potential term.Comment: 5 pages, 5 figure
Scaling of nuclear modification factors for hadrons and light nuclei
The number of constituent quarks (NCQ-) scaling of hadrons and the number of
constituent nucleons (NCN-) scaling of light nuclei are proposed for nuclear
modification factors () of hadrons and light nuclei, respectively,
according to the experimental investigations in relativistic heavy-ion
collisions. Based on coalescence mechanism the scalings are performed for pions
and protons in quark level, and light nuclei and He for
nucleonic level, respectively, formed in Au + Au and Pb + Pb collisions and
nice scaling behaviour emerges. NCQ or NCN scaling law of can be
respectively taken as a probe for quark or nucleon coalescence mechanism for
the formation of hadron or light nuclei in relativistic heavy-ion collisions.Comment: 6 pages, 6 figure
Why Do Firms Evade Taxes? The Role of Information Sharing and Financial Sector Outreach
Informality is a wide-spread phenomenon across the globe. We show that firms in countries with better information sharing systems and greater financial sector outreach evade taxes to a lesser degree, an effect that is stronger for smaller firms, firms in smaller cities and towns, and firms in industries relying more on external financing, with higher liquidity needs and with greater growth potential. However, it is variation in firm size that dominates firm variation in location and industry variation in explaining cross-firm and cross-country variation in tax evasion. This effect is robust to controlling for an array of other measures of the financial and institutional environment firms face. The effect is also robust to controlling for fixed firm effects in a smaller panel dataset of Central and Eastern European countries many of which introduced credit registries or upgraded them in the early 2000s.Formal and informal sector;tax evasion;financial sector development
Reexamining the "finite-size" effects in isobaric yield ratios using a statistical abrasion-ablation model
The "finite-size" effects in the isobaric yield ratio (IYR), which are shown
in the standard grand-canonical and canonical statistical ensembles (SGC/CSE)
method, is claimed to prevent obtaining the actual values of physical
parameters. The conclusion of SGC/CSE maybe questionable for neutron-rich
nucleus induced reaction. To investigate whether the IYR has "finite-size"
effects, the IYR for the mirror nuclei [IYR(m)] are reexamined using a modified
statistical abrasion-ablation (SAA) model. It is found when the projectile is
not so neutron-rich, the IYR(m) depends on the isospin of projectile, but the
size dependence can not be excluded. In reactions induced by the very
neutron-rich projectiles, contrary results to those of the SGC/CSE models are
obtained, i.e., the dependence of the IYR(m) on the size and the isospin of the
projectile is weakened and disappears both in the SAA and the experimental
results.Comment: 5 pages and 4 figure
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