959 research outputs found
Hall effect in laser ablated Co_2(Mn,Fe)Si thin films
Pulsed laser deposition was employed to grow thin films of the Heusler
compounds Co_2MnSi and Co_2FeSi. Epitaxial growth was realized both directly on
MgO (100) and on a Cr or Fe buffer layer. Structural analysis by x-ray and
electron diffraction shows for both materials the ordered L2_1 structure. Bulk
magnetization was determined with a SQUID magnetometer. The values agree with
the Slater-Pauling rule for half-metallic Heusler compounds. On the films grown
directly on the substrate measurements of the Hall effect have been performed.
The normal Hall effect is nearly temperature independent and points towards a
compensated Fermi surface. The anomalous contribution is found to be dominated
by skew scattering. A remarkable sign change of both normal and anomalous Hall
coefficients is observed on changing the valence electron count from 29 (Mn) to
30 (Fe).Comment: 9 pages, 6 figures submitted to J Phys
Local probing of ionic diffusion by electrochemical strain microscopy: spatial resolution and signal formation mechanisms
Electrochemical insertion-deintercalation reactions are typically associated
with significant change of molar volume of the host compound. This strong
coupling between ionic currents and strains underpins image formation
mechanisms in electrochemical strain microscopy (ESM), and allows exploring the
tip-induced electrochemical processes locally. Here we analyze the signal
formation mechanism in ESM, and develop the analytical description of operation
in frequency and time domains. The ESM spectroscopic modes are compared to
classical electrochemical methods including potentiostatic and galvanostatic
intermittent titration (PITT and GITT), and electrochemical impedance
spectroscopy (EIS). This analysis illustrates the feasibility of spatially
resolved studies of Li-ion dynamics on the sub-10 nanometer level using
electromechanical detection.Comment: 49 pages, 17 figures, 4 tables, 3 appendices, to be submitted to J.
Appl. Phys
Diversity and habitat characteristics of macrozoobenthos in the mangrove forest of Lubuk Kertang Village, North Sumatra
Mangrove plays an important role in coastal ecosystems including ecological, social, and economic aspects. This study aimed to determine the diversity of macrozoobenthos and water quality based on diversity index (H?), similarity Index (E), and dominance index (D) in the mangrove of Lubuk Kertang Village North Sumatra, Indonesia. The samples of macrozoobenthos (biological parameter) and water quality (physical and chemical parameters) were collected from fifteen plots in three different stations. Macrozoobenthos were collected in 1 m ? 1 m transect in the mangrove forest. The biota was taken by using a shovel, inserted into a plastic bag, and identified. Results showed that eight species of macrozoobenthos were found and classified into three classes of Gastropod, Bivalvia, and Malacostraca. The highest diversity index (H?) of macrozoobenthos was found at Station II (2.39), the highest evenness index (E) was located at Station I (0.54), and the highest dominance index (D) was found at Station II (0.34). Principal component analysis (PCA) was used to determine the habitat characteristics of macrozoobenthos. PCA confirmed that station III was a habitat with suitable characteristics for the life of macrozoobenthos indicating the negative axis. The present study suggested four parameters namely salinity, clay temperature, and dissolved oxygen that should be preserved to support the survival of macrozoobenthos in the mangrove forests. ? 2018, Society for Indonesian Biodiversity. All rights reservedpublishersversionPeer reviewe
A short-term in vivo model for giant cell tumor of bone
<p>Abstract</p> <p>Background</p> <p>Because of the lack of suitable <it>in vivo </it>models of giant cell tumor of bone (GCT), little is known about its underlying fundamental pro-tumoral events, such as tumor growth, invasion, angiogenesis and metastasis. There is no existing cell line that contains all the cell and tissue tumor components of GCT and thus <it>in vitro </it>testing of anti-tumor agents on GCT is not possible. In this study we have characterized a new method of growing a GCT tumor on a chick chorio-allantoic membrane (CAM) for this purpose.</p> <p>Methods</p> <p>Fresh tumor tissue was obtained from 10 patients and homogenized. The suspension was grafted onto the CAM at day 10 of development. The growth process was monitored by daily observation and photo documentation using <it>in vivo </it>biomicroscopy. After 6 days, samples were fixed and further analyzed using standard histology (hematoxylin and eosin stains), Ki67 staining and fluorescence <it>in situ </it>hybridization (FISH).</p> <p>Results</p> <p>The suspension of all 10 patients formed solid tumors when grafted on the CAM. <it>In vivo </it>microscopy and standard histology revealed a rich vascularization of the tumors. The tumors were composed of the typical components of GCT, including (CD51+/CD68+) multinucleated giant cells whichwere generally less numerous and contained fewer nuclei than in the original tumors. Ki67 staining revealed a very low proliferation rate. The FISH demonstrated that the tumors were composed of human cells interspersed with chick-derived capillaries.</p> <p>Conclusions</p> <p>A reliable protocol for grafting of human GCT onto the chick chorio-allantoic membrane is established. This is the first <it>in vivo </it>model for giant cell tumors of bone which opens new perspectives to study this disease and to test new therapeutical agents.</p
Watching Domains Grow: In-situ studies of polarization switching by combined Scanning Probe and Scanning Transmission Electron Microscopy
Ferroelectric domain nucleation and growth in multiferroic BiFeO3 films is
observed directly by applying a local electric field with a conductive tip
inside a scanning transmission electron microscope. The nucleation and growth
of a ferroelastic domain and its interaction with pre-existing 71^{\circ}
domain walls are observed and compared with the results of phase-field
modeling. In particular, a preferential nucleation site and direction-dependent
pinning of domain walls is observed due to slow kinetics of metastable
switching in the sample without a bottom electrode. These in-situ
spatially-resolved observations of a first-order bias-induced phase transition
reveal the mesoscopic mechanisms underpinning functionality of a wide range of
multiferroic materials
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