Exchange Bias in Bulk α - Fe / γ - Fe 70 Mn 30 Nanocomposites for Permanent Magnet Applications.

Here we report on the microstructural factors influencing the formation of the interfacial exchange bias effect in three-dimensional transition-metal-based nanocomposite systems, with relevance to permanent magnet applications. Bulk phase-separated nanocomposites consisting of the ferromagnetic α -Fe and metastable antiferromagnetic γ - Fe 70 Mn 30 phases exhibit a notable low-temperature exchange bias and substantial coercivity ( H ex = 24.6 kA / m , H C = 95.7 kA / m ) as well as a near room-temperature blocking temperature. Structural investigation by synchrotron X-ray diffraction, neutron scattering, and transmission electron microscopy confirm that the ferromagnetic α -Fe phase nucleates as small precipitates ( d ≈ 50 nm ) at the grain boundaries of the antiferromagnetic γ - Fe 70 Mn 30 grains ( d = 360 - 740 nm ) and grows anisotropically upon heat treatment, resulting in an elliptical geometry. These results indicate that optimization of the exchange bias effect in bulk nanocomposite systems may be achieved through maximizing the surface-to-volume ratio of ferromagnetic precipitates in an antiferromagnetic matrix, enhancing the magnetocrystalline anisotropy of the antiferromagnetic phase to facilitate interfacial pinning and ensuring a balanced distribution of the ferromagnetic and antiferromagnetic phases. This work further clarifies critical factors influencing the formation of an exchange bias in an inexpensive transition-metal-based bulk nanocomposite system with potential for scalable production.

Modified electrical transport probe design for standard magnetometer.

Making electrical transport measurements on a material is often a time consuming process that involves testing a large number of samples. It is thus inconvenient to wire up and rewire samples onto a sample probe. We therefore present a method of modifying Quantum Design's MPMS SQUID magnetometer transport probe that simplifies the process of sample mounting. One of the difficulties to overcome is the small diameter of the sample space. A small socket is designed and mounted on the probe so that various samples mounted on individual headers can be readily exchanged in the socket. We also present some test results on the topological insulator Bi(2)Te(2)Se using the modified probe.

Efficient spin transfer phenomena in Fe/MgO/GaAs structure.

The efficiency of spin polarized charge transfer was investigated in an Fe/MgO tunnel barrier/GaAs based structure using spin dependent photocurrent measurements, whereby a spin imbalance in carrier population was generated in the GaAs by circularly polarized light. The dominance of tunneling transport processes over Schottky emission gave rise to a high spin transfer efficiency of 35% under the photovoltaic mode of device operation. A spin dependent tunneling conductance associated with spin polarized electron transport was identified by the observation of phase changes. This transport prevails over the unpolarized electron and hole conduction over the bias range which corresponds to flat band conditions.

Coexistence of ferromagnetism and superconductivity in Ni/Bi bilayers.

In spite of a lack of superconductivity in bulk crystalline Bi, thin film Bi deposited on thin Ni underlayers are strong-coupled superconductors below approximately 4 K. We unambiguously demonstrate that by tuning the Ni thickness the competition between ferromagnetism and superconductivity in the Ni/Bi can be tailored. For a narrow range of Ni thicknesses, the coexistence of both a superconducting energy gap and conduction electron spin polarization are visible within the Ni side of the Ni/Bi bilayers, independent of any particular theoretical model. We believe that this represents one of the clearest observations of superconductivity and ferromagnetism coexisting.

Advancing paternal age and the risk of schizophrenia.

BACKGROUND: A major source of new mutations in humans is the male germ line, with mutation rates monotonically increasing as father's age at conception advances, possibly because of accumulating replication errors in spermatogonial cell lines. METHOD: We investigated whether the risk of schizophrenia was associated with advancing paternal age in a population-based birth cohort of 87 907 individuals born in Jerusalem from 1964 to 1976 by linking their records to the Israel Psychiatric Registry. RESULTS: Of 1337 offspring admitted to psychiatric units before 1998, 658 were diagnosed as having schizophrenia and related nonaffective psychoses. After controlling for maternal age and other confounding factors (sex, ethnicity, education [to reflect socioeconomic status], and duration of marriage) in proportional hazards regression, we found that paternal age was a strong and significant predictor of the schizophrenia diagnoses, but not of other psychiatric disorders. Compared with offspring of fathers younger than 25 years, the relative risk of schizophrenia increased monotonically in each 5-year age group, reaching 2.02 (95% confidence interval, 1.17-3.51) and 2.96 (95% confidence interval, 1.60-5.47) in offspring of men aged 45 to 49 and 50 years or more, respectively. Categories of mother's age showed no significant effects, after adjusting for paternal age. CONCLUSIONS: These findings support the hypothesis that schizophrenia may be associated, in part, with de novo mutations arising in paternal germ cells. If confirmed, they would entail a need for novel approaches to the identification of genes involved in schizophrenia.

Patient-controlled anesthesia for colonoscopy using propofol: results of a pilot study.

BACKGROUND: We studied the feasibility of using patient-controlled anesthesia (PCA) for conscious sedation during colonoscopy. METHODS: Patients having elective colonoscopy had medications delivered in bolus fashion by PCA pump (Abbot Lifecare Provider 5500 Infusion System). Four patients received propofol as 20 mg/dose boluses, and four patients received propofol in a 0.3 mg/kg/dose. Twelve patients received propofol at 0.2 mg/kg/dose with alfentanil at 4 microg/kg/dose. RESULTS: There were no clinically unacceptable changes in continuously monitored blood pressure, pulse rate, ECG, or respiratory rate. There were no adverse effects from the sedation and no complications due to colonoscopy. Recovery time was rapid, but recall persisted in most subjects. Pain and overall discomfort in patients given propofol only were rated as moderate by most subjects. CONCLUSION: Patient-controlled anesthesia is feasible for use in endoscopic sedation. Propofol alone did not allow adequate pain relief, but propofol and alfentanil together seemed to provide good control of pain.

Mobilferrin is an intermediate in iron transport between transferrin and hemoglobin in K562 cells.

Iron is bound to transferrin in the plasma. A specific receptor on the cell surface binds transferrin and internalizes transferrin and the iron in clathrin-coated pits. These invaginate to form vesicles which release iron to the cytoplasm. Inorganic iron can be transported by an alternative pathway from iron citrate, utilizing a cell surface integrin and a cytoplasmic protein mobilferrin. This article shows that the two pathways donate iron to mobilferrin which acts as an intermediate between the iron bound to transferrin and the incorporation of iron into hemoglobin. Mobilferrin is found associated with the transferrin containing vesicles, and becomes labeled with iron released from transferrin in the vesicles. Mobilferrin is also found in the cytoplasm where pulse-chase experiments show that it, in turn, releases iron to be used for the synthesis of hemoglobin.