Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: a spin-resolved photoemission study

The temperature dependence of the rare-earth Δ2-bulk band has been regarded as an exemplary case which realizes the simple Stoner behavior. We examined the evolution of GdΔ2 bulk bands with temperature in the range 0.5≤ T/TC≤ 1 with spin-resolved, photoemission spectroscopy. The direct observation of the spin-dependent spectral line shapes reveals a complex temperature dependence and manifests a clear inadequacy of the Stoner model to the description of the magnetism in rare earths

Finite temperature magnetism in Gd: evidence against a Stoner behavior

The temperature dependence of the rare-earth valence bands has been regarded as a realization of the Stoner behavior. The exchange splitting of the electronic states appears to scale as the magnetic order parameter for T<TC and to vanish at T = TC. We report here a spin-resolved photoemission study on the evolution of Gd bulk bands for 0.5≤ T/TC≤ 1. The spin-polarized spectral line shapes display a complex temperature dependence, which clearly contrasts with the interpretation of previous experimental results. The spin-resolved photoemission data demonstrate the inadequacy of the Stoner model to the description of magnetism in rare earths

Effect of grain refinement on enhancing critical current density and upper critical field in undoped MgB2 ex-situ tapes

Ex-situ Powder-In-Tube MgB2 tapes prepared with ball-milled, undoped powders showed a strong enhancement of the irreversibility field H*, the upper critical field Hc2 and the critical current density Jc(H) together with the suppression of the anisotropy of all of these quantities. Jc reached 104 A/cm2 at 4.2 K and 10 T, with an irreversibility field of about 14 T at 4.2 K, and Hc2 of 9 T at 25 K, high values for not-doped MgB2. The enhanced Jc and H* values are associated with significant grain refinement produced by milling of the MgB2 powder, which enhances grain boundary pinning, although at the same time also reducing the connectivity from about 12% to 8%. Although enhanced pinning and diminished connectivity are in opposition, the overall influence of ball milling on Jc is positive because the increased density of grains with a size comparable with the mean free path produces strong electron scattering that substantially increases Hc2, especially Hc2 perpendicular to the Mg and B planes.Comment: 26 pages, 9 figures, submitted to J. Appl. Phy

Dietary cadmium intake and risk of cutaneous melanoma: a population-based case-control study in Northern Italy

BACKGROUND AND AIM. Cadmium is a toxic heavy metal for humans, and its environmental exposure has been linked to many adverse health effects, including cancer, atherosclerosis and diabetes. In particular, recent findings suggest that cadmium may increase risk of cutaneous melanoma, possibly through the promotion of the malignant transformation of melanoma cells through aberrant DNA methylation and by inducing gene expression dysregulation. Since in non-occupational exposed and non-smoking subjects dietary exposure is the major source of cadmium exposure, we aimed to assess melanoma risk in relation to dietary cadmium intake. METHODS. We recruited 380 newly-diagnosed incident cases of cutaneous melanoma and 719 sex- and age-matched population controls in four North Italian provinces (Parma, Reggio Emilia, Modena, and Bologna) of Emilia-Romagna Region. We estimated their dietary habits using a semi-quantitative food frequency questionnaire and we evaluated melanoma risk by computing the odds ratio (OR) and its 95% confidence interval (CI) according to quintile distribution of cadmium intake. We used a conditional logistic regression model to compute ORs, matching by sex, age and province of residence, and adjusting also for phototype, non-alcoholic energy intake, body mass index, and Italian Mediterranean Diet Index. Also a spline regression model was used in order to evaluated possible dose-response relation. RESULTS: Median cadmium intake was 5.81 µg/day (interquartile range 4.46-7.59) in cases, and 5.63 µg/day (4.46-7.34) in controls. OR of melanoma associated with 1-unit increase in cadmium intake was 1.11 (95% CI 1.00-1.24). Melanoma risk increased with increasing quintile of cadmium exposure, with ORs of 1.55 (95% CI 0.99-2.42), 1.54 (95% CI 0.99-2-40), 1.75 (95% CI 1.12-2.75), and 1.65 (95% CI 1.05-2.61) from second to highest quintile compared to lowest quintile. Sex-stratified analysis showed substantially comparable results and a generally higher risk in women, with continuous ORs of 1.10 (95% CI 0.93-1-29), and 1.15 (95% CI 0.99-1.33) in men and women, respectively. Spline regression analysis showed a non-linear risk increase, with possible plateau at 5-6 µg/day of cadmium intake. Slightly higher risk estimates in women and older subjects were detected. CONCLUSIONS: Our results seem to point out a positive association between dietary cadmium exposure and melanoma risk in the study population. Such association started to occur at a level of exposure lower than the tolerable intake established for food safety by international authorities

Dietary cadmium exposure and risk of melanoma: an Italian population-based case-control study

Background and aim. The heavy metal cadmium could be highly toxic to humans, and its environmental exposure has been linked to many adverse health effects, such as atherosclerosis, diabetes, and cancer, including melanoma. Although the underlying mechanisms need yet to be clearly identified, recent findings suggested that cadmium can specifically promote the malignant transformation of melanoma cells through the aberrant DNA methylation inducing dysregulation of specific gene expression. Since in the non-occupationally exposed population, in addition to smoking, food intake is the major source of cadmium exposure, we aimed at assessing the risk of cutaneous melanoma in relation to dietary cadmium intake. Methods. Using a population-based study design, we recruited 380 incident cases of newly-diagnosed melanoma and 719 sex- and age-matched controls in the Emilia-Romagna Region, Northern Italy. We evaluated their dietary habits through a semi-quantitative food frequency questionnaire and we computed the odds ratio (OR) and its 95% confidence interval (CI) for melanoma according to quintile distribution of cadmium intake, using a conditional logistic regression model, matching by sex, age and province of residence, and adjusting also for phototype, non-alcoholic energy intake, body mass index, and Italian Mediterranean Diet Index. Results: Median intake of cadmium was 5.81 µg/day (interquartile range 4.46-7.59) in cases, and 5.63 µg/day (4.46-7.34) in controls. OR of melanoma associated with 1-unit increase in cadmium intake was 1.11 (95% CI 1.00-1.24). Melanoma risk increased with increasing quintile of cadmium exposure, with ORs of 1.55 (95% CI 0.99-2.42), 1.54 (95% CI 0.99-2-40), 1.75 (95% CI 1.12-2.75), and 1.65 (95% CI 1.05-2.61) in the second to the highest quintile compared to the lowest quintile. Sex-stratified analysis showed substantially comparable results and a generally higher risk in female population, with continuous ORs of 1.10 (95% CI 0.93-1-29), and 1.15 (95% CI 0.99-1.33) in men and women, respectively. Conclusions: Our results suggest a positive association between cadmium exposure through diet and risk of cutaneous melanoma in a Northern Italy population. Such association started to occur at a level of exposure lower than the tolerable intake established by the World Health Organization, and considered to be safe for humans

Evidence for length-dependent wire expansion, filament dedensification and consequent degradation of critical current density in Ag-alloy sheathed Bi-2212 wires

It is well known that longer Bi-2212 conductors have significantly lower critical current density (Jc) than shorter ones, and recently it has become clear that a major cause of this reduction is internal gas pressure generated during heat treatment, which expands the wire diameter and dedensifies the Bi-2212 filaments. Here we report on the length-dependent expansion of 5 to 240 cm lengths of state-of-the-art, commercial Ag alloy-sheathed Bi-2212 wire after full and some partial heat treatments. Detailed image analysis along the wire length shows that the wire diameter increases with distance from the ends, longer samples often showing evident damage and leaks provoked by the internal gas pressure. Comparison of heat treatments carried out just below the melting point and with the usual melt process makes it clear that melting is crucial to developing high internal pressure. The decay of Jc away from the ends is directly correlated to the local wire diameter increase, which decreases the local Bi-2212 filament mass density and lowers Jc, often by well over 50%. It is clear that control of the internal gas pressure is crucial to attaining the full Jc of these very promising round wires and that the very variable properties of Bi-2212 wires are due to the fact that this internal gas pressure has so far not been well controlled

Fabrication and superconducting properties of multifilamentary MgB2 conductors for AC purposes: twisted tapes and wires with very thin filaments

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