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 $\mathcal{F}_d(n)$ denote the set of minimal permutations of length $n$ with $d$ descents, and let $f_d(n)= |\mathcal{F}_d(n)|$. They derived that $f_{n-2}(n)=2^{n}-(n-1)n-2$ and $f_n(2n)=C_n$, where $C_n$ is the $n$-th Catalan number. Mansour and Yan proved that $f_{n+1}(2n+1)=2^{n-2}nC_{n+1}$. In this paper, we consider the problem of counting minimal permutations in $\mathcal{F}_d(n)$ 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 $2$-regular skew tableaux. Using the determinantal formula for the number of skew Young tableaux of a given shape, we find an explicit formula for $f_{n-3}(n)$. Furthermore, by using the Knuth equivalence, we give a combinatorial interpretation of a formula for a refinement of the number $f_{n+1}(2n+1)$.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 Tl2_2Ba2_2Can−1_{n-1}Cun_nOx_x (n=1,2,3) superconductors

Single crystals of thallium-based cuprates with the general formula Tl$_{2}$Ba$_{2}$Ca$_{n-1}$Cu$_{n}$O$_{x}$(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$_c$. Correspondingly, the ratio of the reflectances below and above T$_{c}$ 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 ($v_2$) and hexadecupole flow ($v_4$) of light clusters have been studied in details for 25 MeV/nucleon $^{86}$Kr + $^{124}$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 ($A$) scaling of the elliptic flow versus transverse momentum ($p_t$) and the scaling of $v_4/A^{2}$ versus $(p_t/A)^2$ have been demonstrated for the light clusters in all above calculation conditions. It was also found that the ratio of $v_4/{v_2}^2$ keeps a constant of 1/2 which is independent of $p_t$ 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 ($R_{cp}$) 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 $d (\bar d)$ and $^3$He for nucleonic level, respectively, formed in Au + Au and Pb + Pb collisions and nice scaling behaviour emerges. NCQ or NCN scaling law of $R_{cp}$ 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