Search results for "Stack"

Slow Magnetization Relaxation in a 1-D Double-Chain Coordination Polymer Composed of {Dy<sup>III</sup> <sub>4</sub>} Repeatin…

2013

The "unsuccessful" synthesis of the non-commercially available 'Dy(O2CPh)3' precursor from the stoichiomet- ric reaction of Dy(NO3)3·5H2O with 3 equivalents of NaO2CPh in MeCN/H2O has led instead to the "successful" isolation and structural characterization of the 1-D coordination polymer (Dy4(O2CPh)12(H2O)8)n·2n(PhCO2H)·n(MeCN) (1·2n(PhCO2H)·n(MeCN)) in excellent yields (~90%). The one-dimensional double-chain structure of 1 was resulted from the linkage of two parallel chains by syn,anti-� 1 :� 1 :μ PhCO2 - groups. The lattice structure of 1 is further extended to a 2-D network through hydrogen bonding and - stacking interactions. The observation of out-of-phase (� �� M) ac susceptibility…

Functionalized Calix[8]arenes, Synthesis and Self-assembly on Graphite

2005

With the intention of building hollow tubular structures by self-assembly, we have designed and successfully synthesized a series of calix[8]arene derivatives. Their phenolic units were functionalized in p-position by various groups which are able to interact via hydrogen bonding or π−π stacking. Ethynyl, amide, urea, or imide links were chosen for the covalent attachment of these functional groups, to ensure the adjustment of an optimal distance for their interaction. Two different kinds of nanostructures self-assembled on a highly oriented pyrolytic graphite (HOPG) surface were found by scanning force microscopy:  parallel aligned nanorods in which the calixarene molecules are adsorbed ed…

Stacking faults in close-packed clusters

2002

Ground state geometries of small hard sphere clusters were studied using two different type of contact interaction, a pair-potential and a many-atom interaction. Monte Carlo method in an FCC lattice with all possible (111) stacking faults was used to obtain the minimum energy geometries for clusters up to 59 atoms. Due to the surface energy, FCC packing is generally favoured as opposite to the HCP structure. However, in most cluster sizes the ground state obtained with the many-atom interaction has one or more stacking faults. The most symmetric geometry is usually not the ground state. Clusters with 59 and 100 atoms were studied due the possibility of a high symmetry cluster with stacking …

Study of the e<sup>+</sup> Distribution in a Layered Stack Sample Using Positron Lifetime Spectroscopy

2010

The results of the Monte Carlo (MC) simulations, using GEANT4 codes, indicate the enhancement of the fraction of the e+ in the denser regions of the sample embedded by the less dense environment. The positron lifetime measurements, performed for two stacks of layers consisting of pure aluminum and silver do not seem to reveal this effect. Some features of the e+ distribution detected in the experiments are not reproduced by the MC simulations.

Fast Axial-Scanning Widefield Microscopy With Constant Magnification and Resolution

2015

In this paper, we propose the use of electrically-addressable lens devices for performing fast non-mechanical axial scanning when imaging three-dimensional samples. This non-mechanical method can be implemented in any commercial microscope. The approach is based on the insertion of the tunable lens at the aperture stop of the microscope objective. By tuning the voltage, a stack of depth images of 3D specimens can be captured in real time and with constant magnification and resolution. The main advantage of our technique is the possibility of performing fast axial scanning free of mechanical vibrations.

Partially Coherent Optical Diffraction Tomography Toward Practical Cell Study

2021

Optical diffraction tomography (ODT) is a computational imaging technique based on refractive index (RI) contrast. Its application for microscopic imaging of weakly absorbing and scattering samples has been demonstrated by using a specially designed holographic microscope with angular scanning of the coherent sample illumination direction. Recently, an alternative low cost technique based on partially coherent sample illumination (PC-ODT), which is compatible with the conventional wide-field transmission microscope, has been established. In this case, the 3D refractive index distribution of the sample is obtained by deconvolution from a single stack of through-focus intensity images. The pe…

Mismatch strain versus dangling bonds: formation of "coin-roll nanowires" by stacking nanosheets.

2010

Low loss microstructured chalcogenide fibers for large non linear effects at 1995 nm

2010

International audience; Microstructured optical fibers (MOFs) are traditionally prepared using the stack and draw technique. In order to avoid the interfaces problems observed in chalcogenide glasses, we have developed a new casting method to prepare the chalcogenide preform. This method allows to reach optical losses around 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various As(38)Se(62) chalcogenide microstructured fibers have been prepared in order to combine large non linear index of these glasses with the mode control offered by MOF structures. Small core fibers have been drawn to enhance the non linearities. In one of these, three Stokes order have been generated by Ram…

Aging of the surface of an Al-Cr-Fe approximant phase in ambient conditions: Chemical composition and physical properties

2003

ABSTRACTWe have investigated the surface properties of quasicrystalline and approximant phases in the Al-(Cu)-Cr-Fe system upon aging in ambient conditions. We found that some of these properties (like the electrochemical behavior, wetting or friction) slowly evolves with the length of exposure to normal atmospheric conditions, reaching a stable state only after several days. This report essentially focuses on one of these alloys, an Al65Cr27Fe8 approximant phase with g-brass structure. In a first part, we describe the effect of aging on the electrochemical behavior of this alloy and we propose an interpretation based on a simple electrical model of the oxidized surface. In a second part, w…

Temperature dependent optical properties of stacked InGaAs/GaAs quantum rings

2008

4 páginas, 3 figuras, 2 tablas.-- MADICA 2006 Conference, Fifth Maghreb-Europe Meeting on Materials and their Applicatons for Devices and Physical, Chemical and Biological Sensors