38 research outputs found
Huge quadratic magneto-optical Kerr effect and magnetization reversal in the CoFeSi Heusler compound
CoFeSi(100) films with L2 structure deposited onto MgO(100) were
studied exploiting both longitudinal (LMOKE) and quadratic (QMOKE)
magneto-optical Kerr effect. The films exhibit a huge QMOKE signal with a
maximum contribution of up to 30 mdeg, which is the largest QMOKE signal in
reflection that has been measured thus far. This large value is a fingerprint
of an exceptionally large spin-orbit coupling of second or higher order. The
CoFeSi(100) films exhibit a rather large coercivity of 350 and 70 Oe for
film thicknesses of 22 and 98 nm, respectively. Despite the fact that the films
are epitaxial, they do not provide an angular dependence of the anisotropy and
the remanence in excess of 1% and 2%, respectively
Magnetic anisotropies and magnetization reversal of the CoCrFeAl Heusler compound
Magnetic anisotropies and magnetization reversal properties of the epitaxial
Heusler compound CoCrFeAl (CCFA) deposited on Fe and Cr
buffer layers are studied. Both samples exhibit a growth-induced fourfold
anisotropy, and magnetization reversal occurs through the formation of stripy
domains or 90 degree domains. During rotational magnetometric scans the sample
deposited on Cr exhibits about 2 degree sharp peaks in the angular dependence
of the coercive field, which are oriented along the hard axis directions. These
peaks are a consequence of the specific domain structure appearing in this
particular measurement geometry. A corresponding feature in the sample
deposited on Fe is not observed.Comment: 11 pages, 7 figure
Ion beam induced modification of exchange interaction and spin-orbit coupling in the CoFeSi Heusler compound
A CoFeSi (CFS) film with L2 structure was irradiated with different
fluences of 30 keV Ga ions. Structural modifications were subsequently
studied using the longitudinal (LMOKE) and quadratic (QMOKE) magneto-optical
Kerr effect. Both the coercivity and the LMOKE amplitude were found to show a
similar behavior upon irradiation: they are nearly constant up to ion fluences
of ion/cm, while they decrease with further
increasing fluences and finally vanish at a fluence of
ion/cm, when the sample becomes paramagnetic. However, contrary to this
behavior, the QMOKE signal nearly vanishes even for the smallest applied
fluence of ion/cm. We attribute this reduction of the
QMOKE signal to an irradiation-induced degeneration of second or higher order
spin-orbit coupling, which already happens at small fluences of 30 keV Ga
ions. On the other hand, the reduction of coercivity and LMOKE signal with high
ion fluences is probably caused by a reduction of the exchange interaction
within the film material
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NERNST: a genetically-encoded ratiometric non-destructive sensing tool to estimate NADP(H) redox status in bacterial, plant and animal systems
NADP(H) is a central metabolic hub providing reducing equivalents to multiple biosynthetic, regulatory and antioxidative pathways in all living organisms. While biosensors are available to determine NADP+ or NADPH levels in vivo, no probe exists to estimate the NADP(H) redox status, a determinant of the cell energy availability. We describe herein the design and characterization of a genetically-encoded ratiometric biosensor, termed NERNST, able to interact with NADP(H) and estimate E NADP(H). NERNST consists of a redox-sensitive green fluorescent protein (roGFP2) fused to an NADPH-thioredoxin reductase C module which selectively monitors NADP(H) redox states via oxido-reduction of the roGFP2 moiety. NERNST is functional in bacterial, plant and animal cells, and organelles such as chloroplasts and mitochondria. Using NERNST, we monitor NADP(H) dynamics during bacterial growth, environmental stresses in plants, metabolic challenges to mammalian cells, and wounding in zebrafish. NERNST estimates the NADP(H) redox poise in living organisms, with various potential applications in biochemical, biotechnological and biomedical research
NERNST: a genetically-encoded ratiometric non-destructive sensing tool to estimate NADP(H) redox status in bacterial, plant and animal systems
NADP(H) is a central metabolic hub providing reducing equivalents to multiple biosynthetic, regulatory and antioxidative pathways in all living organisms. While biosensors are available to determine NADP+ or NADPH levels in vivo, no probe exists to estimate the NADP(H) redox status, a determinant of the cell energy availability. We describe herein the design and characterization of a genetically-encoded ratiometric biosensor, termed NERNST, able to interact with NADP(H) and estimate ENADP(H). NERNST consists of a redox-sensitive green fluorescent protein (roGFP2) fused to an NADPH-thioredoxin reductase C module which selectively monitors NADP(H) redox states via oxidoreduction of the roGFP2 moiety. NERNST is functional in bacterial, plant and animal cells, and organelles such as chloroplasts and mitochondria. Using
NERNST, we monitor NADP(H) dynamics during bacterial growth, environmental stresses in plants, metabolic challenges to mammalian cells, and wounding in zebrafish. NERNST estimates the NADP(H) redox poise in living organisms, with various potential applications in biochemical, biotechnological and biomedical research.Fil: Molinari, Pamela EstefanÃa. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Krapp, Adriana. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Weiner, Andrea MarÃa Julia. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: López, Melina. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Bustos Sanmamed, Pilar. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Tevere, Evelyn. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Calcaterra, Nora B. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Carrillo, Néstor. Universidad Nacional de Rosario. Facultad de Ciencias BioquÃmicas y Farmacéuticas. Instituto de BiologÃa Molecular y Celular de Rosario (IBR-CONICET); Argentina.Fil: Beyer, Hannes M. University of Düsseldorf. Institute of Synthetic Biology; Germany.Fil: Blomeier, Tim.University of Düsseldorf. Institute of Synthetic Biology; Germany.Fil: Zurbriggen, Matias D. University of Düsseldorf. Institute of Synthetic Biology; Germany.Fil: Kondadi, Arun Kumar. Heinrich-Heine-University Düsseldor. Medical Faculty and University Hospital Düsseldorf. Institute of Biochemistry and Molecular Biology I; Germany.Fil: Reichert, Andreas S. Heinrich-Heine-University Düsseldor. Medical Faculty and University Hospital Düsseldorf. Institute of Biochemistry and Molecular Biology I; Germany.Fil: Weber, Wilfried. University of Freiburg. Faculty of Biology and Signalling Research Centres BIOSS and CIBSS; Germany.Fil: Beller, Mathias. University of Düsseldorf. Institute of Mathematical Modeling of Biological Systems; Germany.Fil: Zurbriggen, Matias D. Cluster of Excellence on Plant Sciences; Germany.Fil: Weber, Wilfried. Saarland University. Leibniz Institute for New Materials and Department of Materials Sciences and Engineering; Germany
Facies and faunal assemblage changes in response to the Holocene transgression in the Lagoon of Mayotte (Comoro Archipelago, SW Indian Ocean)
This paper documents the facies change in response to the Holocene transgression within five sediment cores taken in the lagoon of Mayotte, which contain a Type-1 depositional sequence (lowstand, transgressive and highstand deposits underlain by an erosive sequence boundary). Quantitative compositional analysis and visual examination of the bioclasts were used to document the facies changes. The distribution of the skeletal and non-skeletal grains in the lagoon of Mayotte is clearly controlled by (1) the rate and amplitude of the Holocene sea-level rise, (2) the pre-Holocene basement topography and (3) the growth-potential of the barrier reef during sea-level rise, and the changes in bathymetry and continuity during this period. The sequence boundary consists of the glacial karst surface. The change-over from the glacial lowstand is marked by the occurrence of mangrove deposits. Terrigenous and/or mixed terrigenous-carbonate muds to sandy muds with a mollusc or mollusc-ostracod assemblage dominate the transgressive deposits. Mixed carbonate-siliciclastic or carbonate sand to gravel with a mollusc-foraminifer or mollusc-coral-foraminifer assemblage characterize the early highstand deposits on the inner lagoonal plains. The early highstand deposits in the outer lagoonal plains consist of carbonate muds with a mollusc-foraminifer assemblage. Late highstand deposits consist of terrigenous muds in the nearshore bays, mixed terrigenous-carbonate sandy muds to sands with a mollusc-foraminifer assemblage on the inner lagoonal plains and mixed muds with a mollusc-foraminifer assemblage on the outer deep lagoonal plains. The present development stage of the individual lagoons comprises semi-enclosed to open lagoons with fair or good water exchange with the open ocean
Influence of microenvironment on engraftment of transplanted β-cells
Pancreatic islet transplantation into the liver provides a possibility to treat selected patients with brittle type 1 diabetes mellitus. However, massive early β-cell death increases the number of islets needed to restore glucose homeostasis. Moreover, late dysfunction and death contribute to the poor long-term results of islet transplantation on insulin independence. Studies in recent years have identified early and late challenges for transplanted pancreatic islets, including an instant blood-mediated inflammatory reaction when exposing human islets to the blood microenvironment in the portal vein and the low oxygenated milieu of islets transplanted into the liver. Poor revascularization of remaining intact islets combined with severe changes in the gene expression of islets transplanted into the liver contributes to late dysfunction. Strategies to overcome these hurdles have been developed, and some of these interventions are now even tested in clinical trials providing a hope to improve results in clinical islet transplantation. In parallel, experimental and clinical studies have, based on the identified problems with the liver site, evaluated the possibility of change of implantation organ in order to improve the results. Site-specific differences clearly exist in the engraftment of transplanted islets, and a more thorough characterization of alternative locations is needed. New strategies with modifications of islet microenvironment with cells and growth factors adhered to the islet surface or in a surrounding matrix could be designed to intervene with site-specific hurdles and provide possibilities to improve future results of islet transplantation
The Use of Biomaterials in Islet Transplantation
Pancreatic islet transplantation is a therapeutic option to replace destroyed β cells in autoimmune diabetes. Islets are transplanted into the liver via the portal vein; however, inflammation, the required immunosuppression, and lack of vasculature decrease early islet viability and function. Therefore, the use of accessory therapy and biomaterials to protect islets and improve islet function has definite therapeutic potential. Here we review the application of niche accessory cells and factors, as well as the use of biomaterials as carriers or capsules, for pancreatic islet transplantation
Exchange interaction and magnetic domain formation in periodically inhomogeneous magnetic media
We investigate the formation of magnetic domains in a magnetic trilayer patterned using ion beam bombardment. The system consists of a finite array of in-plane magnetized ferromagnetic Fe elements embedded into an antiferromagnetically coupled Fe∕Cr∕Fe trilayer. Varying the interelement distance, we observe by means of magnetic force microscopy an intriguing transition from individual to collective behavior of the array elements. Above a critical interelement spacing, strong interelement coupling effects are observed, leading to complex correlations between domain structure on individual elements. The mechanism driving these correlations is the formation of domain boundary walls between elements, contrary to the more commonly observed dipolar coupling effects in magnetic arrays fabricated using lithography. Below this critical spacing, the entire array behaves as a single magnetic entity, exhibiting a collective magnetic domain state. The experimental observations can be simulated numerically and explained using an analytical model. The model correctly predicts observed dependencies on interelement distances