Estimation of the charge carrier localization length from Gaussian fluctuations in the magneto-thermopower of La_{0.6}Y_{0.1}Ca_{0.3}MnO_3

The magneto-thermoelectric power (TEP) $\Delta S(T,H)$ of perovskite type manganise oxide $La_{0.6}Y_{0.1}Ca_{0.3}MnO_3$ is found to exhibit a sharp peak at some temperature $T^{*}=170K$. By approximating the true shape of the measured magneto-TEP in the vicinity of $T^{*}$ by a linear triangle of the form $\Delta S(T,H)\simeq S_p(H)\pm B^{\pm}(H)(T^{*}-T)$, we observe that $B ^{-}(H)\simeq 2B ^{+}(H)$. We adopt the electron localization scenario and introduce a Ginzburg-Landau (GL) type theory which incorporates the two concurrent phase transitions, viz., the paramagnetic-ferromagnetic transition at the Curie point $T_C$ and the "metal-insulator" (M-I) transition at $T_{MI}$. The latter is characterized by the divergence of the field-dependent charge carrier localization length $\xi (T,H)$ at some characteristic field $H_0$. Calculating the average and fluctuation contributions to the total magnetization and the transport entropy related magneto-TEP $\Delta S(T,H)$ within the GL theory, we obtain a simple relationship between $T^{*}$ and the above two critical temperatures ($T_{C}$ and $T_{MI}$). The observed slope ratio $B ^{-}(H)/B ^{+}(H)$ is found to be governed by the competition between the electron-spin exchange $JS$ and the induced magnetic energy $M_sH_0$. The comparison of our data with the model predictions produce $T_{C}=195K$, $JS=40meV$, $M_0=0.4M_s$, $\xi_0=10\AA$, and $n_e/n_i=2/3$ for the estimates of the Curie temperature, the exchange coupling constant, the critical magnetization, the localization length, and the free-to-localized carrier number density ratio, respectively.Comment: 6 pages (REVTEX), 2 PS figures (epsf.sty); submitted to Phys.Rev.

Benford's law predicted digit distribution of aggregated income taxes: the surprising conformity of Italian cities and regions

The yearly aggregated tax income data of all, more than 8000, Italian municipalities are analyzed for a period of five years, from 2007 to 2011, to search for conformity or not with Benford's law, a counter-intuitive phenomenon observed in large tabulated data where the occurrence of numbers having smaller initial digits is more favored than those with larger digits. This is done in anticipation that large deviations from Benford's law will be found in view of tax evasion supposedly being widespread across Italy. Contrary to expectations, we show that the overall tax income data for all these years is in excellent agreement with Benford's law. Furthermore, we also analyze the data of Calabria, Campania and Sicily, the three Italian regions known for strong presence of mafia, to see if there are any marked deviations from Benford's law. Again, we find that all yearly data sets for Calabria and Sicily agree with Benford's law whereas only the 2007 and 2008 yearly data show departures from the law for Campania. These results are again surprising in view of underground and illegal nature of economic activities of mafia which significantly contribute to tax evasion. Some hypothesis for the found conformity is presented.Comment: 18 pages, 5 tables, 4 figures, 61 references, To appear in European Physical Journal

Permanent 125I-seed prostate brachytherapy: early prostate specific antigen value as a predictor of PSA bounce occurrence

<p>Abstract</p> <p>Purpose</p> <p>To evaluate predictive factors for PSA bounce after ¹²⁵I permanent seed prostate brachytherapy and identify criteria that distinguish between benign bounces and biochemical relapses.</p> <p>Materials and methods</p> <p>Men treated with exclusive permanent ¹²⁵I seed brachytherapy from November 1999, with at least a 36 months follow-up were included. Bounce was defined as an increase ≥ 0.2 ng/ml above the nadir, followed by a spontaneous return to the nadir. Biochemical failure (BF) was defined using the criteria of the Phoenix conference: nadir +2 ng/ml.</p> <p>Results</p> <p>198 men were included. After a median follow-up of 63.9 months, 21 patients experienced a BF, and 35.9% had at least one bounce which occurred after a median period of 17 months after implantation (4-50). Bounce amplitude was 0.6 ng/ml (0.2-5.1), and duration was 13.6 months (4.0-44.9). In 12.5%, bounce magnitude exceeded the threshold defining BF. Age at the time of treatment and high PSA level assessed at 6 weeks were significantly correlated with bounce but not with BF. Bounce patients had a higher BF free survival than the others (100% versus 92%, p = 0,007). In case of PSA increase, PSA doubling time and velocity were not significantly different between bounce and BF patients. Bounces occurred significantly earlier than relapses and than nadir + 0.2 ng/ml in BF patients (17 vs 27.8 months, p < 0.0001).</p> <p>Conclusion</p> <p>High PSA value assessed 6 weeks after brachytherapy and young age were significantly associated to a higher risk of bounces but not to BF. Long delays between brachytherapy and PSA increase are more indicative of BF.</p

Cloning and characterization of AOEB166, a novel mammalian antioxidant enzyme of the peroxiredoxin family.

Using two-dimensional electrophoresis, we have recently identified in human bronchoalveolar lavage fluid a novel protein, termed B166, with a molecular mass of 17 kDa. Here, we report the cloning of human and rat cDNAs encoding B166, which has been renamed AOEB166 for antioxidant enzyme B166. Indeed, the deduced amino acid sequence reveals that AOEB166 represents a new mammalian subfamily of AhpC/TSA peroxiredoxin antioxidant enzymes. Human AOEB166 shares 63% similarity with Escherichia coli AhpC22 alkyl hydroperoxide reductase and 66% similarity with a recently identified Saccharomyces cerevisiae alkyl hydroperoxide reductase/thioredoxin peroxidase. Moreover, recombinant AOEB166 expressed in E. coli exhibits a peroxidase activity, and an antioxidant activity comparable with that of catalase was demonstrated with the glutamine synthetase protection assay against dithiothreitol/Fe3+/O(2) oxidation. The analysis of AOEB166 mRNA distribution in 30 different human tissues and in 10 cell lines shows that the gene is widely expressed in the body. Of interest, the analysis of N- and C-terminal domains of both human and rat AOEB166 reveals amino acid sequences presenting features of mitochondrial and peroxisomal targeting sequences. Furthermore, human AOEB166 expressed as a fusion protein with GFP in HepG2 cell line is sorted to these organelles. Finally, acute inflammation induced in rat lung by lipopolysaccharide is associated with an increase of AOEB166 mRNA levels in lung, suggesting a protective role for AOEB166 in oxidative and inflammatory processes

Kinetic studies of peroxiredoxin 6 from <i>Arenicola marina</i>: rapid oxidation by hydrogen peroxide and peroxynitrite but lack of reduction by hydrogen sulfide

Arenicola marina lives in marine environments where hydrogen peroxide concentrations reach micromolar levels. The annelid also forms reactive species through metabolic pathways. Its antioxidant systems include a cytosolic peroxiredoxin, peroxiredoxin 6 (AmPrx6 or AmPRDX6) that shows high homology to the mammalian 1-Cys peroxiredoxin. Previous work confirmed the peroxidase activity of AmPrx6 in the presence of dithiotreitol. Herein, we performed an in vitro kinetic characterization of the recombinant enzyme. AmPrx6 reduced hydrogen peroxide and peroxynitrite with rate constants of 1.1 × 107 and 2 × 106 M-1 s-1, respectively, at pH 7.4 and 25 °C. Reduction of tert-butyl hydroperoxide was slower. The pKa of the peroxidatic thiol of AmPrx6 was determined as 5.1 ± 0.2, indicating that it exists as thiolate, the reactive species, at physiological pH. The reductive part of the catalytic cycle was also explored. Hydrogen sulfide, present in millimolar concentrations in marine sediments where the annelid lives and that is able to reduce the mammalian 1-Cys peroxiredoxin, did not support AmPrx6 peroxidase activity. The enzyme was not reduced by other potential physiological reductants tested. Our data indicate that in this annelid, Prx6 could contribute to peroxide detoxification in the presence of a so far unidentified reducing counterpart

Critical behaviour of transport coefficients at a structural-ferromagnetic transition

Accurate measurements of the electrical resistivity, the thermoelectric power and the thermal conductivity of TbZn are reported at the ferromagnetic-structural transition. The temperature derivative of the coefficients is examined. The critical behaviours are understood in terms of conduction electron scattering on spin correlated fluctuations and the presence of structural and magnetic domains