Resonant tunneling magnetoresistance in epitaxial metal-semiconductor heterostructures

We report on resonant tunneling magnetoresistance via localized states through a ZnSe semiconducting barrier which can reverse the sign of the effective spin polarization of tunneling electrons. Experiments performed on Fe/ZnSe/Fe planar junctions have shown that positive, negative or even its sign-reversible magnetoresistance can be obtained, depending on the bias voltage, the energy of localized states in the ZnSe barrier and spatial symmetry. The averaging of conduction over all localized states in a junction under resonant condition is strongly detrimental to the magnetoresistance

UPO Biobank: The Challenge of Integrating Biobanking into the Academic Environment to Support Translational Research

Biobanks are driving motors of precision and personalized medicine by providing high-quality biological material/data through the standardization and harmonization of their collection, preservation, and distribution. UPO Biobank was established in 2020 as an institutional, disease, and population biobank within the University of Piemonte Orientale (UPO) for the promotion and support of high-quality, multidisciplinary studies. UPO Biobank collaborates with UPO researchers, sustaining academic translational research, and supports the Novara Cohort Study, a longitudinal cohort study involving the population in the Novara area that will collect data and biological specimens that will be available for epidemiological, public health, and biological studies on aging. UPO Biobank has been developed by implementing the quality standards for the field and the ethical and legal issues and normative about privacy protection, data collection, and sharing. As a member of the "Biobanking and Biomolecular Resources Research Infrastructure" (BBMRI) network, UPO Biobank aims to expand its activity worldwide and launch cooperation with new national and international partners and researchers. The objective of this manuscript is to report an institutional and operational experience through the description of the technical and procedural solutions and ethical and scientific implications associated with the establishment of this university research biobank

Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer

We have put into evidence the existence of an antiferromagnetic coupling between iron epilayers separated by a ZnSe crystalline semiconductor. The effect has been observed for ZnSe spacers thinner than 4 nm at room-temperature. The coupling constant increases linearly with temperature with a constant slope of ~5.5x 10-9 J/m2K. The mechanisms that may explain such exchange interaction are discussed in the manuscript. It results that thermally-induced effective exchange coupling mediated by spin-dependent on and off resonant tunnelling of electrons via localized mid-gap defect states in the ZnSe spacer layer appears to be the most plausible mechanism to induce the antiferromagnetic coupling.Comment: 29 pages, 8 figure

Spin-dependent resonant quantum tunneling between magnetic nanoparticles on a macroscopic length scale

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Macroscopic quantum phenomena are common features observed in superconductors, superfluid helium, and Bose-Einstein condensates. However, most of quantum transport studies are based on a small number of dots and are not in long-range electron transport length scale. Here we show that spin-dependent resonant quantum tunneling is achieved in the macroscopic length scale (a few millimeters) corresponding to an array of up to 10(4) junctions in a series consisting of Co nanoparticles embedded in an oxygen-deficient TiO(2) matrix. This phenomenon is observed by magnetoresistance measurements at 5 K in a Coulomb blockade regime. We further present a model based on resonant spin-polarized quantum tunneling of electrons of Co particles. It occurs through resonant continuous spin-polarized defect band states located near the Fermi level of the defective TiO(2), which acts as a magnetic tunnel barrier. These results might be potentially useful for future designs of spintronic quantum devices.834Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Magnetoresistance in granular magnetic tunnel junctions with Fe nanoparticles embedded in ZnSe semiconducting epilayer

We have investigated transport properties of iron (Fe) nanoparticles embedded in zinc selenide (ZnSe) semiconducting epilayers prepared by molecular beam epitaxy. Both positive and negative tunneling magnetoresistances (TMRs) were measured depending on the applied voltage biases and on the temperature. A slow reduction of the TMR magnitude with temperature was detected and it could be explained in terms of a crossover between direct/resonant tunneling and variable range hopping. The temperature behavior of the magnetoresistance is a clear signature of tunneling and hopping mechanisms mediated by the ZnSe barrier localized states. (C) 2008 American Institute of Physics.1031

The satisfactory growth and development at 2 years of age of the INTERGROWTH-21st Fetal Growth Standards cohort support its appropriateness for constructing international standards.

BACKGROUND: The World Health Organization recommends that human growth should be monitored with the use of international standards. However, in obstetric practice, we continue to monitor fetal growth using numerous local charts or equations that are based on different populations for each body structure. Consistent with World Health Organization recommendations, the INTERGROWTH-21st Project has produced the first set of international standards to date pregnancies; to monitor fetal growth, estimated fetal weight, Doppler measures, and brain structures; to measure uterine growth, maternal nutrition, newborn infant size, and body composition; and to assess the postnatal growth of preterm babies. All these standards are based on the same healthy pregnancy cohort. Recognizing the importance of demonstrating that, postnatally, this cohort still adhered to the World Health Organization prescriptive approach, we followed their growth and development to the key milestone of 2 years of age. OBJECTIVE: The purpose of this study was to determine whether the babies in the INTERGROWTH-21st Project maintained optimal growth and development in childhood. STUDY DESIGN: In the Infant Follow-up Study of the INTERGROWTH-21st Project, we evaluated postnatal growth, nutrition, morbidity, and motor development up to 2 years of age in the children who contributed data to the construction of the international fetal growth, newborn infant size and body composition at birth, and preterm postnatal growth standards. Clinical care, feeding practices, anthropometric measures, and assessment of morbidity were standardized across study sites and documented at 1 and 2 years of age. Weight, length, and head circumference age- and sex-specific z-scores and percentiles and motor development milestones were estimated with the use of the World Health Organization Child Growth Standards and World Health Organization milestone distributions, respectively. For the preterm infants, corrected age was used. Variance components analysis was used to estimate the percentage variability among individuals within a study site compared with that among study sites. RESULTS: There were 3711 eligible singleton live births; 3042 children (82%) were evaluated at 2 years of age. There were no substantive differences between the included group and the lost-to-follow up group. Infant mortality rate was 3 per 1000; neonatal mortality rate was 1.6 per 1000. At the 2-year visit, the children included in the INTERGROWTH-21st Fetal Growth Standards were at the 49th percentile for length, 50th percentile for head circumference, and 58th percentile for weight of the World Health Organization Child Growth Standards. Similar results were seen for the preterm subgroup that was included in the INTERGROWTH-21st Preterm Postnatal Growth Standards. The cohort overlapped between the 3rd and 97th percentiles of the World Health Organization motor development milestones. We estimated that the variance among study sites explains only 5.5% of the total variability in the length of the children between birth and 2 years of age, although the variance among individuals within a study site explains 42.9% (ie, 8 times the amount explained by the variation among sites). An increase of 8.9 cm in adult height over mean parental height is estimated to occur in the cohort from low-middle income countries, provided that children continue to have adequate health, environmental, and nutritional conditions. CONCLUSION: The cohort enrolled in the INTERGROWTH-21st standards remained healthy with adequate growth and motor development up to 2 years of age, which supports its appropriateness for the construction of international fetal and preterm postnatal growth standards

Planar assembly of monodisperse metallic cobalt nanoparticles embedded in TiO2-delta matrix

International audienceWe report the growth of a single layer of metallic cobalt nanoparticles in a TiO2-delta matrix. The films are grown by pulsed laser deposition ( PLD). Transmission electron microscopy ( TEM) is used to determine the morphology of the system and the crystalline structure ( HCP and/ or FCC) of the cobalt nanoparticles. A sharp interface between the nanoparticles and the matrix is observed. Electron energy loss spectroscopy ( EELS) is used to investigate the metallic character of the cobalt. Oxidation of cobalt at the interface with the matrix is not observed. With regards to the importance of the matrix for transport properties and because of the great variability of the oxygen content of TiO2-delta, efforts were also made on the analysis of TiO2-delta matrix. EELS measurements indicate an oxygen deficiency with respect to the nominal TiO2 composition which increases with growth temperature. This leads to a rather low resistivity of the matrix which also decreases with increasing growth temperature