Search results for "Microscopy"
showing 10 items of 3390 documents
Field-induced tip–sample oxygen transfer in scanning tunneling microscopy on TiO2(110) (1 1).
2008
International audience; A study on the field-induced tip–surface oxygen transfer at room temperature and its influence on the tunneling conditions for stable STM imaging of the TiO2(110) (1 1) surface is reported. A simple model of field-induced transfer is applied to tungsten and platinum–iridium tips. The oxygen transition rates from the sample to the tip or from the tip to the sample depend on the oxygen desorption barriers formed at tunneling distance. For stable imaging the applied bias voltage has to balance the oxygen transfer probabilities in both directions. In the case of Pt/Ir tips, the tunneling conditions for images with clear evidence of bridging oxygen point defects have been…
Engineering 3D ordered molecular thin films by a nanoscale control
2010
This perspective aims to report on experimental preparation and investigation tools for engineering molecular thin films with a three-dimensional (3D) nanoscale control that is of relevant interest for different emerging applications as well as for the development of calibration standards. Such thin films may be obtained by man-made methods, self-assembly or spatio-temporal self-organization and/or by the combination of these last approaches with external tools. Understanding the main features and the physical-chemistry underlying the related ordering phenomena is in due course and a theoretical framework is under development. In this respect it is of fundamental importance to achieve the a…
Structure determination and homogeneous optical properties of CdS/HgS quantum dots
1997
The structural and optical properties of heterogeneous semiconductor nanoparticles consisting of CdS and HgS are investigated by High Resolution Electron Microscopy (HRTEM) and selective spectroscopy like Hole Burning (HB) and Fluorescence Line Narrowing (FLN). The HRTEM study shows that epitaxy is possible in nanocrystals, provided the crystallites have well defined faceted shapes to begin with. From the HB- and FLN experiments homogeneous absorption and fluorescence spectra are calculated. It could be shown that the absorption is coupled to HgS-like phonons (250 cm -1 ) whereas the emission frequency is closer to the LO phonon frequency of CdS.
Serotoninergic innervation of nonprincipal cells in the cerebral cortex of the lizard Podarcis hispanica.
2004
The mechanism of serotoninergic transmission in the neo- and archicortex of mammals kis complex, including both synaptic and nonsynaptic components, direct actions on principal cells, and indirect effects mediated by GABAergic interneurons. Here we studied the termination pattern and synaptic organization of the serotoninergic afferents in the cerebral cortex of the lizard, Podarcis hispanica, which is considered to correspond in part to the mammalian hippocampal formation, with the aim of unraveling basic, phylogenetically preserved rules in the connectivity of this pathway. We demonstrate that serotoninergic afferents, visualized by immunostaining for serotonin itself, establish multiple …
Minireview: Nicotinic Acetylcholine Receptors on Hippocampal Neurons: Distribution on the Neuronal Surface and Modulation of Receptor Activity
1997
The recent development of a technique that uses infrared microscopy for the visualization of well-defined areas on the surface of neurons, and a computerized system of micromanipulators led to the discovery that functional nicotinic acetylcholine receptors (nAChRs) are expressed at higher density on the dendrites than on the soma of rat hippocampal neurons. The finding that the expression of alpha-bungarotoxin-sensitive, alpha 7-bearing, nAChRs and dihydro-beta-erythroidine-sensitive, alpha 4 beta 2 nAChRs tends to increase along the dendritic length suggests that these receptors may be highly involved in the integration of synaptic functions in hippocampal neurons. The present report also …
Characterization ofBacillus thuringiensisserovarbolivia(serotype H63), a novel serovar isolated from the Bolivian high valleys
1999
The type strain Bacillus thuringiensis var. bolivia (serotype H63), isolated from the Bolivian high valleys, has been characterized at different levels. Its parasporal crystal has an unusual shape and it is composed of a protein of 155 kDa which shows two bands of 75 and 80 kDa after activation. Analysis by PCR shows the presence of cry1 genes, and amplification with specific primers gave products for cry1 E, cry1 D, cry4 A and cry4 B with sizes different to those expected. Immunoblotting tests showed positive reaction for Cry1 E, Cry3 A, Cry4 A and Cry11 A crystal proteins. The plasmid pattern revealed two large and two small plasmids. Toxicity tests were performed against 14 insects and a…
First description of nonmotileVibrio vulnificusstrains virulent for eels
2007
Nonmotile Vibrio vulnificus strains were isolated as pure cultures from body ulcers and internal organs of wild diseased European eels caught in a Mediterranean freshwater coastal lagoon. All 54 V. vulnificus isolates were nonmotile, indole-, ornithine decarboxilase-, mannitol- and cellobiose-positive, developed the opaque variant in culture, belonged to the O-antigenic serovar A and were highly virulent for eels by both intraperitoneal injection and immersion challenges. The nonmotile phenotype found in our V. vulnificus isolates was stable: nonmotile cells were always recovered from experimentally infected eels; no variation in the immobility of the V. vulnificus cells was observed for re…
Shedding of Membrane Vesicles Mediates Fibroblast Growth Factor-2 Release from Cells
2003
Fibroblast growth factor-2 (FGF-2), a polypeptide with regulatory activity on cell growth and differentiation, lacks a conventional secretory signal sequence, and its mechanism of release from cells remains unclear. We characterized the role of extracellular vesicle shedding in FGF-2 release. Viable cells released membrane vesicles in the presence of serum. However, in serum-free medium vesicle shedding was dramatically down-regulated, and the cells did not release FGF-2 activity into their conditioned medium. Addition of serum to serum-starved cells rapidly induced intracellular FGF-2 clustering under the plasma membrane and into granules that colocalized with patches of the cell membrane …
OPLA scaffold, collagen I, and horse serum induce a higher degree of myogenic differentiation of adult rat cardiac stem cells
2009
In the last few years, a major goal of cardiac research has been to drive stem cell differentiation to replace damaged myocardium. Several research groups have attempted to differentiate potential cardiac stem cells (CSCs) using bi- or three-dimensional systems supplemented with growth factors or molecules acting as differentiating substances. We hypothesize that these systems failed to induce a complete differentiation because they lacked an architectural space. In the present study, we isolated a pool of small proliferating and fibroblast-like cells from adult rat myocardium. The phenotype of these cells was assessed and the characterized cells were cultured in a collagen I/OPLA scaffold …
Leaf epicuticular waxes effects egg parasitoid’s response to host adult footprint contact kairomone
2009
Chemical footprints left behind by true bugs are perceived as a contact kairomones by scelionid egg parasitoids. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, previous studies have shown that the kairomone mediating such behavior is part of N. viridula’s cuticular hydrocarbons. In this study, the effect of epicuticular waxes of leaves of broad bean, Vicia faba, on wasp response to footprints of N. viridula females are investigated. Plants with intact waxes layer were used (1) without host chemical contamination, or (2) contaminated by host female footprints. Mechanically de-waxed plants were tested (3) without host chemical contamination, or (4) de-waxed a few min…