Inductive effects of 10 and 12-vertex closo-carborane anions: cluster size and charge make a difference

2016 ◽  
Vol 52 (9) ◽  
pp. 1824-1826 ◽  
Author(s):  
Jess Estrada ◽  
Christopher A. Lugo ◽  
Scott G. McArthur ◽  
Vincent Lavallo
Keyword(s):  
Cluster Size ◽  
Inductive Effects ◽  
Electron Donating Groups ◽  
First Time ◽  
Carborane Anions

The inductive effects of 10 and 12-vertex closo-carborane anion ligand substituents are elucidated for the first time. It is found that both of these cluster substituents are potent electron donating groups, which is in contrast to C-functionalized o-carborane. The fact that the 10-vertex cluster displays the strongest electron donating ability can be rationalized by its charge and size.

Cluster Formation in thin Au Films Near the Metalinsulator Transition

1982 ◽  
Vol 40 ◽  
pp. 732-733
Author(s):  
E.I. Alessandrini ◽  
R.B. Laibowitz ◽  
C.R. Guarnieri ◽  
R.F. Voss ◽  
D.S. MacLachlan
Keyword(s):  
Size Distribution ◽  
Percolation Theory ◽  
Cluster Size ◽  
Cluster Formation ◽  
Insulator Transition ◽  
Analysis Program ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Resistivity Measurements ◽  
First Time

Recently we have reported that measurements of the cluster size distribution near the metal-insulator transition in thin cermet Al-Al2O3 films show good quantative agreement with the predictions of 2 dimensional percolation theory. In this paper, we present an investigation of thin Au films (a non-oxidizing metal) near the metal-insulator transition and correlate the structure with electrical resistivity measurements. The TEM micrographs at different film thicknesses were digitized and computer enhanced. An automatic cluster analysis program was used for the the first time to identify clusters and compile size distribution for comparison with percolation theory.

Depth resolution at organic interfaces sputtered by argon gas cluster ions: the effect of energy, angle and cluster size

The Analyst ◽  
2015 ◽  
Vol 140 (19) ◽  
pp. 6508-6516 ◽  
Author(s):  
M. P. Seah ◽  
S. J. Spencer ◽  
R. Havelund ◽  
I. S. Gilmore ◽  
A. G. Shard
Keyword(s):  
Cluster Size ◽  
Depth Resolution ◽  
Cluster Ions ◽  
Operating Parameters ◽  
Organic Analysis ◽  
Argon Gas ◽  
Organic Interfaces ◽  
First Time

This paper presents, for the first time, the different operating parameters defining the best depth resolution in SIMS organic analysis.

Why are Fluorene-Containing Materials so Versatile? An Electronic Structure Perspective

2008 ◽  
Vol 61 (12) ◽  
pp. 981 ◽  
Author(s):  
Igor Novak ◽  
Branka Kovač
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Charge Transfer ◽  
Theoretical Framework ◽  
Photoelectron Spectra ◽  
Ionization Energies ◽  
Transfer Processes ◽  
Inductive Effects ◽  
Linear Optical Properties ◽  
First Time

The HeI/HeII photoelectron spectra of substituted fluorenes (2-aminofluorene, 2,7-dibromofluorene, 2-acetylfluorene, and 9-trimethylsilylfluorene) are reported for the first time. We have observed significant changes in the π-electronic structure of the title molecules on substitution at 2-, 7-, and 9-positions and interpreted them within the theoretical framework of resonance and inductive effects. The substituents attached to fluorene at these positions govern the photophysical behaviour and properties of polymetallaynes that contain the fluorene moiety. The mediated properties include the size of the polymer bandgap, various non-linear optical properties, and the intensity and lifetime of luminescence processes. Our spectral results provide some detailed explanations of substituent influences in the form of, for example, orbital ionization energies, which can be further related to charge-transfer processes present in these metallo-organic polymers.

Experimental Study of Cluster Size Effect with Size-selected Cluster Ion Beam System

2003 ◽  
Vol 792 ◽  
Author(s):  
Noriaki Toyoda ◽  
Shingo Houzumi ◽  
Takaaki Aoki ◽  
Isao Yamada
Keyword(s):  
Cluster Size ◽  
Ion Beam ◽  
Oxide Thickness ◽  
Magnetic Flux Density ◽  
Cluster Ion ◽  
Gas Cluster Ion Beam ◽  
Dynamics Simulations ◽  
Ion Current Density ◽  
First Time ◽  
Good Agreement

ABSTRACTA size-selected gas cluster ion beam (GCIB) system has been developed to study the size effects of energetic large cluster ion bombardments on a solid surface for the first time. This system equipped a permanent magnet with a magnetic flux density of 1.2 T. There is a sliding detector and sample holder on a guiding rail perpendicular to the incoming cluster beam axis. By locating a sample at a certain position, particular size of cluster ion can be irradiated continuously with affordable ion current density. When the total acceleration energy of Ar-GCIB was 5keV, both amorphous and oxide thickness on Si substrate increased with decreasing cluster size. This result showed good agreement with that obtained from molecular dynamics simulations.

scholarly journals Substituent effect on lysozyme-catalysed hydrolysis of some β-aryl di-N-acetylchitobiosides

1969 ◽  
Vol 114 (3) ◽  
pp. 529-534 ◽  
Author(s):  
C. S. Tsai ◽  
J. Y. Tang ◽  
S. C. Subbarao
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Substituent Effect ◽  
Deuterium Isotope Effect ◽  
Catalytic Rate ◽  
Electron Donating Groups ◽  
First Time ◽  
Kinetics Of ◽  
Hydrolysis Of

Measurements are reported on the kinetics of the lysozyme-catalysed hydrolysis of several β-aryl di-N-acetylchitobiosides, some of which have been synthesized for the first time. The catalytic rate constants (kcat.) at 45° yield a curved Hammett plot (concave up) and the plot of ΔH‡ versus ΔS‡ has a sharp break. Substrates with electron-withdrawing groups exhibit a kinetic deuterium isotope effect (kHcat./kDcat.), whereas those with electron-donating groups show no such isotope effect. The results suggest the operation of different mechanisms for the two types of substrates.

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

Annulate lamellae in the Sertoli cells of guinea pig testis after unilateral torsion of the spermatic cord

1984 ◽  
Vol 42 ◽  
pp. 196-197
Author(s):  
J. Chakraborty ◽  
A. P. Sinha Hikim ◽  
J. S. Jhunjhunwala
Keyword(s):  
Sertoli Cells ◽  
Guinea Pigs ◽  
Spermatic Cord ◽  
Present Report ◽  
Cell Types ◽  
Annulate Lamellae ◽  
Spermatogenic Cells ◽  
Electron Microscopic ◽  
Structural Details ◽  
First Time

Although the presence of annulate lamellae was noted in many cell types, including the rat spermatogenic cells, this structure was never reported in the Sertoli cells of any rodent species. The present report is based on a part of our project on the effect of torsion of the spermatic cord to the contralateral testis. This paper describes for the first time, the fine structural details of the annulate lamellae in the Sertoli cells of damaged testis from guinea pigs.One side of the spermatic cord of each of six Hartly strain adult guinea pigs was surgically twisted (540°) under pentobarbital anesthesia (1). Four months after induction of torsion, animals were sacrificed, testes were excised and processed for the light and electron microscopic investigations. In the damaged testis, the majority of seminiferous tubule contained a layer of Sertoli cells with occasional spermatogonia (Fig. 1). Nuclei of these Sertoli cells were highly pleomorphic and contained small chromatinic clumps adjacent to the inner aspect of the nuclear envelope (Fig. 2).

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

1991 ◽  
Vol 49 ◽  
pp. 956-957 ◽  
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Diamond Films ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Dark Field ◽  
Growth Surface ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
First Time ◽  
Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

A microscopic marker experiment study on high temperature oxidation of Ni-Al alloy

1986 ◽  
Vol 44 ◽  
pp. 514-515
Author(s):  
Shou-kong Fan
Keyword(s):  
Transport Mechanism ◽  
High Temperature Oxidation ◽  
Transverse Section ◽  
Al Alloy ◽  
Metal Interface ◽  
Electron Microscopic ◽  
Temperature Oxidation ◽  
Analytical Electron ◽  
Microscopic Studies ◽  
First Time

Transmission and analytical electron microscopic studies of scale microstructures and microscopic marker experiments have been carried out in order to determine the transport mechanism in the oxidation of Ni-Al alloy. According to the classical theory, the oxidation of nickel takes place by transport of Ni cations across the scale forming new oxide at the scale/gas interface. Any markers deposited on the Ni surface are expected to remain at the scale/metal interface after oxidation. This investigation using TEM transverse section techniques and deposited microscopic markers shows a different result,which indicates that a considerable amount of oxygen was transported inward. This is the first time that such fine-scale markers have been coupled with high resolution characterization instruments such as TEM/STEM to provide detailed information about evolution of oxide scale microstructure.

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