Search results for "magnetism."
showing 10 items of 1879 documents
Strong Exchange Coupling in a Trimetallic Radical-Bridged Cobalt(II)-Hexaazatrinaphthylene Complex.
2016
Reducing hexaazatrinaphthylene (HAN) with potassium in the presence of 18-c-6 produces [{K(18-c-6)}HAN], which contains the S=1/2 radical [HAN](.-) . The [HAN](.-) radical can be transferred to the cobalt(II) amide [Co{N(SiMe3 )2 }2 ], forming [K(18-c-6)][(HAN){Co(N'')2 }3 ]; magnetic measurements on this compound reveal an S=4 spin system with strong cobalt-ligand antiferromagnetic exchange and J≈-290 cm(-1) (-2 J formalism). In contrast, the Co(II) centres in the unreduced analogue [(HAN){Co(N'')2 }3 ] are weakly coupled (J≈-4.4 cm(-1) ). The finding that [HAN](.-) can be synthesized as a stable salt and transferred to cobalt introduces potential new routes to magnetic materials based on …
Demo 48. Histéresis magnética
2013
Objetivo: Mostrar la presencia de dominios magnéticos en un medio ferromagnético, su evolución en presencia de un campo magnético externo, visualizando el fenómeno de histéresis.
Fe and Zn co-substituted beta-tricalcium phosphate (β-TCP): Synthesis, structural, magnetic, mechanical and biological properties
2020
This work was supported by the European Social Fund under the No. 09.3.3- LMT-K-712 “Development of Competences of Scientists, other Researchers and Students through Practical Research Activities” measure. AK would like to express sincere gratitude for Fellowship administrated by The Japan Society for the Promotion of Science (JSPS). Fellow’s ID No.: L12546. Authors are grateful to R. Vargalis (Vilnius University) for taking SEM images. © 2020. This work is licensed under a CC BY-NC-ND license.
Geminal parahydrogen-induced polarization: accumulating long-lived singlet order on methylene proton pairs
2020
In the majority of hydrogenative parahydrogen-induced polarization (PHIP) experiments, the hydrogen molecule undergoes pairwise cis addition to an unsaturated precursor to occupy vicinal positions on the product molecule. However, some ruthenium-based hydrogenation catalysts induce geminal hydrogenation, leading to a reaction product in which the two hydrogen atoms are transferred to the same carbon centre, forming a methylene (CH2) group. The singlet order of parahydrogen is substantially retained over the geminal hydrogenation reaction, giving rise to a singlet-hyperpolarized CH2 group. Although the T1 relaxation times of the methylene protons are often short, the singlet order has a long…
Enhanced Permeability and Retention-like Extravasation of Nanoparticles from the Vasculature into Tuberculosis Granulomas in Zebrafish and Mouse Mode…
2018
The enhanced permeability and retention (EPR) effect is the only described mechanism enabling nanoparticles (NPs) flowing in blood to reach tumors by a passive targeting mechanism. Here, using the transparent zebrafish model infected with Mycobacterium marinum we show that an EPR-like process also occurs allowing different types of NPs to extravasate from the vasculature to reach granulomas that assemble during tuberculosis (TB) infection. PEGylated liposomes and other NP types cross endothelial barriers near infection sites within minutes after injection and accumulate close to granulomas. Although similar to 100 and 190 nm NPs concentrated most in granulomas, even similar to 700 nm liposo…
Barrier properties of chitosan coated polyethylene
2012
The transfer properties of chitosan coated polyethylene (PE) films were studied. The barrier properties of non coated PE were not affected by relative humidity changes. The presence of the hydrophilic chitosan layer acted as a water reservoir on the polyethylene film surface which significantly promoted its sensitivity to the water vapour. The water vapour permeability increased 1.85 times at a higher RH. Coated PE films showed more than two-order decrease in the oxygen permeability (PO2) and three-order-decrease in the carbon dioxide permeability (PCO2). When the chitosan coated PE surface was exposed to the water vapour, the PO2 and the PCO2 were significantly increased. However, the perm…
Coordination-Induced Spin-State Switching with Nickel Chlorin and Nickel Isobacteriochlorin
2015
We present the first coordination-induced spin-state switching with nickel chlorin and nickel isobacteriochlorin. The spin-state switching was monitored by UV-vis spectroscopy and NMR titration experiments. The association constants (K1 and K2) and thermodynamic parameters (ΔH and ΔS) of the coordination of pyridine were determined. The first X-ray analyses of a paramagnetic nickel chlorin and a nickel isobacteriochlorin provide further information about the structure of the octahedral complexes. Nickel chlorin and even more pronounced nickel isobacteriochlorin exhibit stronger coordination of axial ligands compared to the corresponding nickel porphyrin and thus provide the basis for more e…
A discourse on human hair fibers and reflections on the conservation of drug molecules
1996
A gross discourse on human hair fibers and their formation is presented stressing the various interdisciplinary aspects, such as the morphological, biological, structural and biochemical data considered to be important in the field of hair analysis. An attempt is made to explain the incorporation of drug molecules during hair fiber formation by using the classical concepts of drug absorption based on lipoid theory and the pH-partition hypothesis as well as a modern biological approach on the permeability of cell membranes. In addition to the physiochemical considerations of the transport properties of a particular drug molecule such as a) the lipophilicity, which determines permeability thr…
Direct detection of 17O NMR in [Gd(DOTA)]- by NMR Spectroscopy
2015
The 17O NMR spectrum of the non-coordinated carboxyl oxygen in the GdIII-DOTA (DOTA = tetraazacyclododecanetetraacetic acid) complex has been observed experimentally. Its line width is essentially unaffected by paramagnetic relaxation due to gadolinium, and is only affected by the quadrupole pathway. The results are supported by the relevant parameters (hyperfine and quadrupole coupling constants) calculated by relativistic DFT methods. This finding opens up new avenues for investigating the structure and reactivity of paramagnetic GdIII complexes used as contrast agents in magnetic resonance imaging.
Finnish Secondary Students’ Mental Models of Magnetism
2020
We examined Finnish lower secondary students’ mental models of magnetism through their drawings, written explanations and interviews. Secondary students in Finland (N=12) engaged in six lessons designed specifically to target three key concepts in understanding magnetism: structure and organization (magnetic domains), magnetic fields and magnetic interactions. We describe how, with a finite number of key concepts introduced, students reflected upon and revised their mental models of magnetism and magnetic interactions towards more sophisticated and normative scientific views. We found two new categories of students’ models: the pole model and pole/field model. The critical moments in evolvi…