X-ray structures and luminescence properties of Co(II) and Co(III) complexes of cofacial diporphyrins

2003 ◽  
Vol 07 (07) ◽  
pp. 474-483 ◽  
Author(s):  
Frédéric Bolze ◽  
Marc Drouin ◽  
Pierre D. Harvey ◽  
Claude P. Gros ◽  
Enrique Espinosa ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Structural Data ◽  
Previous Literature ◽  
The Other ◽  
Luminescence Properties ◽  
X Ray ◽  
Face To Face ◽  
Other Hand

The crystal structures of two face-to-face diporphyrin compounds based upon the DPA ligand (1,8-bis(5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethyl-porphyrinyl))anthracene), i.e. H 4( DPA ) and ( DPA ) Co 2 are reported. The structural data are compared to that of other bimetallic DPA systems, and diporphyrinic Co complexes. In addition, the luminescence properties of ( OEP ) Co ( OEP = 2,3,7,8,12,13,17,18-octaethylporphyrin), H 2( DPA ) Co , H 2( DPA )( CoIm ) O 2, ( DPA ) Co 2, ( DPA )( CoIm )2 O 2 are reported, where Im is 1-t-butyl-5-phenyl imidazole. Contrary to previous literature reports, the Co (II) species are found to be weakly luminescent, where fluorescence is detected for both the mono- and diporphyrinic systems, and is assigned to emissions arising from the lowest 1 Q (ππ*) states, while phosphorescence is detected at 77 K only for the monoporphyrin species, ( OEP ) Co . On the other hand, the Co (III) complexes are not luminescent.

scholarly journals White Dwarf Masses and Accretion Rates of Recurrent Novae: an X-ray Perspective

2011 ◽  
Vol 7 (S281) ◽  
pp. 186-189
Author(s):  
Koji Mukai ◽  
Jennifer L. Sokoloski ◽  
Thomas Nelson ◽  
Gerardo J. M. Luna
Keyword(s):  
White Dwarf ◽  
Cataclysmic Variables ◽  
The Other ◽  
X Ray ◽  
Other Hand ◽  
Accretion Rates

AbstractWe present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RNe candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

An Overview of the Interdiffusion Studies in Mo-Si and W-Si Systems

2014 ◽  
Vol 354 ◽  
pp. 79-83
Author(s):  
Soumitra Roy ◽  
Soma Prasad ◽  
Aloke Paul
Keyword(s):  
Crystal Structures ◽  
Atomic Number ◽  
Diffusion Coefficients ◽  
Relative Increase ◽  
The Other ◽  
Reactive Diffusion ◽  
Refractory Elements ◽  
Other Hand ◽  
Two Systems ◽  
Diffusion Rates

The growth of phases by reactive diffusion in Mo-Si and W-Si systems are compared. The crystal structures of MSi2 and M5Si3 phases (M = Mo, W) are similar in these two systems. However, the diffusion rates of the components change systematically with a change in the atomic number. Integrated diffusion coefficients in both phases increase with an increasing atomic number of refractory elements i.e. from Mo to W. On the other hand, the ratio of diffusivities of the components decreases. This indicates a relative increase in the diffusion rates of the metal components with increasing atomic number and a difference in defects concentrations in these two systems.

Structural Studies on N-(2,4,6-Trimethylphenyl)-methyl/ chloro-acetamides, 2,4,6-(CH3)3C6H2NH-CO-CH3–yXy (X = CH3 or Cl and y = 0, 1, 2)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 588-594 ◽  
Author(s):  
Basavalinganadoddy Thimme Gowda ◽  
Jozef Kožíšek ◽  
Hartmut Fuess
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structural Data ◽  
The Other ◽  
Side Chain ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
Lattice Constants ◽  
Peptide Linkage ◽  
The Mean

TMPAThe effect of substitutions in the ring and in the side chain on the crystal structure of N- (2,4,6-trimethylphenyl)-methyl/chloro-acetamides of the configuration 2,4,6-(CH3)3C6H2NH-COCH3− yXy (X = CH3 or Cl and y = 0,1, 2) has been studied by determining the crystal structures of N-(2,4,6-trimethylphenyl)-acetamide, 2,4,6-(CH3)3C6H2NH-CO-CH3 (); N-(2,4,6- trimethylphenyl)-2-methylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2-CH3 (TMPMA); N-(2,4,6- trimethylphenyl)-2,2-dimethylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH(CH3)2 (TMPDMA) and N-(2,4,6-trimethylphenyl)-2,2-dichloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CHCl2 (TMPDCA). The crystallographic system, space group, formula units and lattice constants in Å are: TMPA: monoclinic, Pn, Z = 2, a = 8.142(3), b = 8.469(3), c = 8.223(3), β = 113.61(2)◦; TMPMA: monoclinic, P21/n, Z = 8, a = 9.103(1), b = 15.812(2), c = 16.4787(19), α = 89.974(10)◦, β = 96.951(10)◦, γ =89.967(10)◦; TMPDMA: monoclinic, P21/c, Z = 4, a =4.757(1), b= 24.644(4), c =10.785(2), β = 99.647(17)◦; TMPDCA: triclinic, P¯1, Z = 2, a = 4.652(1), b = 11.006(1), c = 12.369(1), α = 82.521(7)◦, β = 83.09(1)◦, γ = 79.84(1)◦. The results are analyzed along with the structural data of N-phenylacetamide, C6H5NH-CO-CH3; N-(2,4,6-trimethylphenyl)-2-chloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)-acetamide, 2,4,6-Cl3C6H2NH-COCH3; N-(2,4,6-trichlorophenyl)-2-chloroacetamide, 2,4,6-Cl3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)- 2,2-dichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CHCl2 and N-(2,4,6-trichlorophenyl)- 2,2,2-trichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CCl3. TMPA, TMPMA and TMPDCA have one molecule each in their asymmetric units, while TMPDMA has two molecules in its asymmetric unit. Changes in the mean ring distances are smaller on substitution as the effect has to be transmitted through the peptide linkage. The comparison of the other bond parameters reveal that there are significant changes in them on substitution.

scholarly journals Consequences of COVID-19 on my experiment of gene overexpression in beans

2021 ◽  
Vol 39 (4) ◽  
Author(s):  
Salma Sarai González-Meléndez
Keyword(s):  
Subcellular Location ◽  
Confocal Microscope ◽  
The Other ◽  
Research Center ◽  
Gene Overexpression ◽  
Research Centers ◽  
Experimental Phase ◽  
Face To Face ◽  
Other Hand ◽  
At Home

<p>My name is Salma Meléndez and I am currently a graduate in Agrogenomic Sciences. In March 2020, when COVID-19 was detected in Mexico, I was in my eighth semester of my undergraduate degree. At that time, he had an experiment of overexpression of a gene in bean roots, in order to explore its function during symbiosis with rhizobial bacteria. Unfortunately, the laboratory and the entire campus canceled their face-to-face activities in order to reduce the risk of contagion. An alternative was to take the experimental plants to my house to give the proper care, however, the situation became difficult as I did not have the space or the required conditions at home. On the other hand, other research centers with which we had collaboration agreements also canceled access, such is the case of the Optical Research Center, where we used the confocal microscope to detect subcellular location of proteins. The closure of institutions allowed me to write theoretical parts of my thesis, however, the experimental phase was definitely affected for at least six months. The experiment with the plants was almost completely lost. In the subsequent months I had the opportunity to re-enter my institution; however, under strict conditions and on staggered days, which made certain measurements that require daily continuity difficult. Currently, the laboratory is not as it used to look, full of colleagues sharing results and difficulties, exchanging advice and even certain materials. I think the pandemic has pushed us to do our work more individually and slowly. Consequently, my degree was delayed and transferred from 2020 to 2021. There are still many challenges to overcome, although activities have not been fully restored, science does not stop and we have found a way to face it, slowly but surely.</p>

Synthesis of ZrO2 Nanotubes by Anodization of Zr Foil

2015 ◽  
Vol 799-800 ◽  
pp. 125-129
Author(s):  
Mary Donnabelle L. Balela ◽  
April Alexa S. Lagarde ◽  
Stephen Jann A. Tamayo ◽  
Nikko S. Villareal ◽  
Ann Marielle Parreno
Keyword(s):  
Aqueous Solution ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Preparation ◽  
The Other ◽  
Preparation Methods ◽  
X Ray ◽  
Anodization Time ◽  
Other Hand ◽  
Scanning Electron

Zirconia (ZrO2) nanotubes were synthesized by anodization of zirconium (Zr) foil in NH4Fand (NH4)2SO4 aqueous solution. Different surface preparation methods (electropolishing and etching) were applied on the Zr foil prior to anodizaton. In addition, the anodization time and NH4F concentration were varied. The structure and morphologies of the nanotubes and their crystallinity were confirmed using scanning electron microscope and x-ray diffractometer, respectively. ZrO2 nanotubes with large diameters and thick walls were formed at lower NH4F concentration and longer anodization time. On the other hand, smaller nanotubes with thinner walls were produced when the NH4F concentration was increased. The synthesized nanotubes were predominantly tetragonal ZrO2 with small amounts of monoclinic ZrO2.

Polymorphs of phenazine hexacyanoferrate(II) hydrate: supramolecular isomerism in a 2D hydrogen-bonded network

2021 ◽  
Vol 77 (2) ◽  
pp. 211-218
Author(s):  
Ivica Cvrtila ◽  
Vladimir Stilinović
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
The Other ◽  
Two Dimensional ◽  
Structural Motifs ◽  
Supramolecular Isomerism ◽  
Other Hand ◽  
Π Stacking ◽  
Hydrogen Bonded

The crystal structures of two polymorphs of a phenazine hexacyanoferrate(II) salt/cocrystal, with the formula (Hphen)3[H2Fe(CN)6][H3Fe(CN)6]·2(phen)·2H2O, are reported. The polymorphs are comprised of (Hphen)2[H2Fe(CN)6] trimers and (Hphen)[(phen)2(H2O)2][H3Fe(CN)6] hexamers connected into two-dimensional (2D) hydrogen-bonded networks through strong hydrogen bonds between the [H2Fe(CN)6]2− and [H3Fe(CN)6]− anions. The layers are further connected by hydrogen bonds, as well as through π–π stacking of phenazine moieties. Aside from the identical 2D hydrogen-bonded networks, the two polymorphs share phenazine stacks comprising both protonated and neutral phenazine molecules. On the other hand, the polymorphs differ in the conformation, placement and orientation of the hydrogen-bonded trimers and hexamers within the hydrogen-bonded networks, which leads to different packing of the hydrogen-bonded layers, as well as to different hydrogen bonding between the layers. Thus, aside from an exceptional number of symmetry-independent units (nine in total), these two polymorphs show how robust structural motifs, such as charge-assisted hydrogen bonding or π-stacking, allow for different arrangements of the supramolecular units, resulting in polymorphism.

Distribution of Calcium and Phosphate in Cells of the Enamel Organ in the Rat Lower Incisor

1987 ◽  
Vol 1 (2) ◽  
pp. 236-244 ◽  
Author(s):  
T. Kawamoto ◽  
M. Shimizu
Keyword(s):  
The Other ◽  
Whole Body ◽  
Enamel Organ ◽  
Maturation Stage ◽  
Lower Incisor ◽  
X Ray ◽  
Other Hand ◽  
Freeze Dried ◽  
Significant Difference ◽  
Cell Layers

The distribution of calcium and phosphate in the cells of the enamel organ of the rat lower incisors was investigated by autoradiography and energy-dispersive x-ray spectrometry (EDS). Radioactive calcium or phosphate was injected i.p. into seven-day-old rats of the Wistar strain. The animals were frozen 0.5, 1, and 10 min after injection, and embedded in 5% carboxymethyl cellulose. Sagittal sections of 10 μm thickness were made in which the lower incisor was included as a part of the whole-body section. For autoradiography, the sections were freeze-dried and placed in contact with dry thin films prepared from autoradiographic emulsion. For EDS, sections were mounted on carbon stubs, freeze-dried, coated with carbon, and examined by EDS in a SEM. 45Ca and 32P autoradiograms showed that the radioactivity was located over the papillary layer cells adjacent to the secretory stage ameloblasts and was much higher here than in the ameloblastic layer. On the other hand, there was no significant difference between the amount of radioactivity of these two cell layers in the maturation stage, although higher radioactivity was detectable in the maturation stage enamel than in the secretory stage enamel. Pronounced Ka x-ray peaks were obtained for P, S, Cl, and K originating from the cells of the papillary and ameloblastic layers in the secretory stage, but only very low peaks were obtained for Ca. On the other hand, in addition to these elements, remarkably high Ca and Fe peaks could be detected in the ameloblastic layer of the maturation stage.

scholarly journals Year-scale Morphological Variation of the X-ray Crab Nebula

2004 ◽  
Vol 218 ◽  
pp. 181-184 ◽  
Author(s):  
Koji Mori ◽  
David N. Burrows ◽  
George G. Pavlov ◽  
J. Jeff Hester ◽  
Shinpei Shibata ◽  
...  
Keyword(s):  
Morphological Variation ◽  
Crab Nebula ◽  
The Other ◽  
X Ray ◽  
Morphological Variations ◽  
Other Hand ◽  
Pulsar Wind ◽  
Circular Structures ◽  
The Crab Nebula

We present year-scale morphological variations of the Crab Nebula revealed by the Chandra X-ray Observatory. Observations have been performed about every 1.7 years over the three years from launch. The variations are clearly recognized at two sites: the torus and the southern jet. The torus, which had been steadily expanding until 1.7 years ago, now appears to have shrunk in the latest observation. Additionally, the circular structures seen to the northeast of the torus have decayed into several arcs. On the other hand, the southern jet shows the growth of its overall kinked-structure. We discuss the nature of these variations in terms of the pulsar wind nebula mechanism.

Configuration of Quadrivalent Atoms

1929 ◽  
Vol 25 (2) ◽  
pp. 219-221
Author(s):  
T. M. Lowry
Keyword(s):  
The Other ◽  
Tetrahedral Configuration ◽  
X Ray ◽  
Metallic Atom ◽  
Other Hand ◽  
Function Change ◽  
The One ◽  
Image Position ◽  
Octahedral Configuration ◽  
As If

Two alternative views have been expressed in regard to the configuration of quadrivalent atoms. On the one hand le Bel and van't Hoff assigned to quadrivalent carbon a tetrahedral configuration, which has since been confirmed by the X-ray analysis of the diamond. On the other hand, Werner in 1893 adopted an octahedral configuration for radicals of the type MA6, e.g. inand then suggested that “the molecules [MA4]X2 are incomplete molecules [MA6]X2. The radicals [MA4] result from the octahedrally-conceived radicals [MA6] by loss of two groups A, but with no function-change of the acid residue…. They behave as if the bivalent metallic atom in the centre of the octahedron could no longer bind all six of the groups A and lost two of them leaving behind the fragment [MA4]” (p. 303).

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