On the possibility of spontaneous currents in mesoscopie systems

It is shown that a mesoscopic metallic system can exhibit a phase transition to a low temperature state with a spontaneous orbital current if it is sufficiently free of elastic defect scattering. The interaction among the electrons, which is the reason of the phase transition, is of the magnetic origin and it leads to an ordered state of the orbital magnetic moments

Manipulating nonequilibrium magnetism through superconductors

Electrostatic control of the magnetization of a normal mesoscopic conductor is analyzed in a hybrid superconductor-normal-superconductor system. This effect stems from the interplay between the non-equilibrium condition in the normal region and the Zeeman splitting of the quasiparticle density of states of the superconductor subjected to a static in-plane magnetic field. Unexpected spin-dependent effects such as magnetization suppression, diamagnetic-like response of the susceptibility as well as spin-polarized current generation are the most remarkable features presented. The impact of scattering events is evaluated and let us show that this effect is compatible with realistic material properties and fabrication techniques.Comment: 5 pages, 4 figure

Comment on "Experimental determination of superconducting parameters for the intermetallic perovskite superconductor MgCNi3_3"

In a recent paper (Phys. Rev. {\bf B 67}, 094502 (2003)) Mao et al. investigated the bias-dependent conductance of mechanical junctions between superconducting MgCNi$_3$ and a sharp W tip. They interpreted their results in terms of 'single-particle tunneling'. We show it is more likely that current transport through those junctions is determined by thermal effects due to the huge normal-state resistivity of MgCNi$_3$. Therefore no conclusion can be drawn about the possible unconventional pairing or strong-coupling superconductivity in MgCNi$_3$.Comment: 2 pages, 1 Fig. Comment on Z. Q. Mao et al. (Phys. Rev. {\bf B 67}, 094502 (2003)

Current-Carrying Ground States in Mesoscopic and Macroscopic Systems

We extend a theorem of Bloch, which concerns the net orbital current carried by an interacting electron system in equilibrium, to include mesoscopic effects. We obtain a rigorous upper bound to the allowed ground-state current in a ring or disc, for an interacting electron system in the presence of static but otherwise arbitrary electric and magnetic fields. We also investigate the effects of spin-orbit and current-current interactions on the upper bound. Current-current interactions, caused by the magnetic field produced at a point r by a moving electron at r, are found to reduce the upper bound by an amount that is determined by the self-inductance of the system. A solvable model of an electron system that includes current-current interactions is shown to realize our upper bound, and the upper bound is compared with measurements of the persistent current in a single ring.Comment: 7 pager, Revtex, 1 figure available from [email protected]

Thermal expansion, heat capacity and magnetostriction of RAl3_3 (R = Tm, Yb, Lu) single crystals

We present thermal expansion and longitudinal magnetostriction data for cubic RAl3 (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl3 is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl3 show crystal electric field contributions and have strong magnetic field dependencies. de Haas-van Alphen-like oscillations were observed in the magnetostriction data of YbAl3 and LuAl3, several new extreme orbits were measured and their effective masses were estimated. Zero and 140 kOe specific heat data taken on both LuAl3 and TmAl3 for T < 200 K allow for the determination of a CEF splitting scheme for TmAl3

The Preparation Temperature Influences the Physicochemical Nature and Activity of Nanoceria

Cerium oxide nanoparticles, so-called nanoceria, are engineered nanomaterials prepared by many methods that result in products with varying physicochemical properties and applications. Those used industrially are often calcined, an example is NM-212. Other nanoceria have beneficial pharmaceutical properties and are often prepared by solvothermal synthesis. Solvothermally synthesized nanoceria dissolve in acidic environments, accelerated by carboxylic acids. NM-212 dissolution has been reported to be minimal. To gain insight into the role of high-temperature exposure on nanoceria dissolution, product susceptibility to carboxylic acid-accelerated dissolution, and its effect on biological and catalytic properties of nanoceria, the dissolution of NM-212, a solvothermally synthesized nanoceria material, and a calcined form of the solvothermally synthesized nanoceria material (ca. 40, 4, and 40 nm diameter, respectively) was investigated. Two dissolution methods were employed. Dissolution of NM-212 and the calcined nanoceria was much slower than that of the non-calcined form. The decreased solubility was attributed to an increased amount of surface Ce4+ species induced by the high temperature. Carboxylic acids doubled the very low dissolution rate of NM-212. Nanoceria dissolution releases Ce3+ ions, which, with phosphate, form insoluble cerium phosphate in vivo. The addition of immobilized phosphates did not accelerate nanoceria dissolution, suggesting that the Ce3+ ion release during nanoceria dissolution was phosphate-independent. Smaller particles resulting from partial nanoceria dissolution led to less cellular protein carbonyl formation, attributed to an increased amount of surface Ce3+ species. Surface reactivity was greater for the solvothermally synthesized nanoceria, which had more Ce3+ species at the surface. The results show that temperature treatment of nanoceria can produce significant differences in solubility and surface cerium valence, which affect the biological and catalytic properties of nanoceria

Biokinetics and effects of barium sulfate nanoparticles

Background: Nanoparticulate barium sulfate has potential novel applications and wide use in the polymer and paint industries. A short-term inhalation study on barium sulfate nanoparticles (BaSO4 NPs) was previously published [Part Fibre Toxicol 11:16, 2014]. We performed comprehensive biokinetic studies of 131BaSO4 NPs administered via different routes and of acute and subchronic pulmonary responses to instilled or inhaled BaSO4 in rats. Methods: We compared the tissue distribution of 131Ba over 28 days after intratracheal (IT) instillation, and over 7 days after gavage and intravenous (IV) injection of 131BaSO4. Rats were exposed to 50 mg/m3 BaSO4 aerosol for 4 or 13 weeks (6 h/day, 5 consecutive days/week), and then gross and histopathologic, blood and bronchoalveolar lavage (BAL) fluid analyses were performed. BAL fluid from instilled rats was also analyzed. Results: Inhaled BaSO4 NPs showed no toxicity after 4-week exposure, but a slight neutrophil increase in BAL after 13-week exposure was observed. Lung burden of inhaled BaSO4 NPs after 4-week exposure (0.84 ± 0.18 mg/lung) decreased by 95% over 34 days. Instilled BaSO4 NPs caused dose-dependent inflammatory responses in the lungs. Instilled BaSO4 NPs (0.28 mg/lung) was cleared with a half-life of ≈ 9.6 days. Translocated 131Ba from the lungs was predominantly found in the bone (29%). Only 0.15% of gavaged dose was detected in all organs at 7 days. IV-injected 131BaSO4 NPs were predominantly localized in the liver, spleen, lungs and bone at 2 hours, but redistributed from the liver to bone over time. Fecal excretion was the dominant elimination pathway for all three routes of exposure. Conclusions: Pulmonary exposure to instilled BaSO4 NPs caused dose-dependent lung injury and inflammation. Four-week and 13-week inhalation exposures to a high concentration (50 mg/m3) of BaSO4 NPs elicited minimal pulmonary response and no systemic effects. Instilled and inhaled BaSO4 NPs were cleared quickly yet resulted in higher tissue retention than when ingested. Particle dissolution is a likely mechanism. Injected BaSO4 NPs localized in the reticuloendothelial organs and redistributed to the bone over time. BaSO4 NP exhibited lower toxicity and biopersistence in the lungs compared to other poorly soluble NPs such as CeO2 and TiO2. Electronic supplementary material The online version of this article (doi:10.1186/s12989-014-0055-3) contains supplementary material, which is available to authorized users

Possibility of long-range order in clean mesoscopic cylinders

A microscopic Hamiltonian of the magnetostatic interaction is discussed. This long-range interaction can play an important role in mesoscopic systems leading to an ordered ground state. The self-consistent mean field approximation of the magnetostatic interaction is performed to give an effective Hamiltonian from which the spontaneous, self-sustaining currents can be obtained. To go beyond the mean field approximation the mean square fluctuation of the total momentum is calculated and its influence on self-sustaining currents in mesoscopic cylinders with quasi-1D and quasi-2D conduction is considered. Then, by the use of the microscopic Hamiltonian of the magnetostatic interaction for a set of stacked rings, the problem of long-range order is discussed. The temperature $T^{*}$ below which the system is in an ordered state is determined.Comment: 14 pages, REVTeX, 5 figures, in print in Phys. Rev.