Ionic Interactions in Actinide Tetrahalides

2001 ◽  
Vol 56 (5) ◽  
pp. 376-380 ◽  
Author(s):  
Z. Akdeniz ◽  
A. Karaman ◽  
M. P. Tosi
Keyword(s):  
Vibrational Mode ◽  
Dynamic Structure ◽  
Potential Energy Function ◽  
The Other ◽  
Ionic Interactions ◽  
Ionic Character ◽  
Force Model ◽  
Electronic Polarizability ◽  
Actinide Series ◽  
High Degree

Abstract We determine a model of the ionic interactions in AX 4 compounds (where A is an atom in the actinide series from Th to Am and X = F, Cl, Br or I) by an analysis of data on the static and dynamic structure of their molecular monomers. The potential energy function that we adopt is taken from earlier work on rare-earth trihalides [Z. Akdeniz, Z. Q q e k and M. P. Tosi, Z. Naturforsch. 55a, 861 (2000)] and in particular allows for the electronic polarizability of the actinide ion. This polarizability quantitatively determines the antisymmetric-bending vibrational mode, but its magnitude remains compatible with a symmetric tetrahedral shape of the molecule at equilibrium. The fluorides have an especially high degree of ionic character, and the interionic-force parameters for each halide of the U, Np, Pu and Am series show regular trends, suggesting that extrapolations to the other transuranic-element halides may usefully be made. The Th compounds show some deviations from these trends, and the interionic-force model that we determine for ThCl4 differs somewhat from that obtained in a previous study. We therefore return on the evaluation of the relative stability of charged oligomers of ThCl4 and ZrCl4 and find confirmation of our earlier results on this problem.

Ionic Interactions in Lanthanide Halides

2000 ◽  
Vol 55 (11-12) ◽  
pp. 861-866 ◽  
Author(s):  
Z. Akdeniz ◽  
Z. Çiçek ◽  
M. P. Tosia
Keyword(s):  
Rare Earth ◽  
Metal Ion ◽  
Essential Element ◽  
Dynamic Structure ◽  
Potential Energy Function ◽  
Electron Diffraction Data ◽  
Ionic Interactions ◽  
Electric Polarizability ◽  
Rare Earth Series ◽  
The Rare Earth

Abstract We determine a model of the ionic interactions in RX3 compounds (where R is a metal in the rare-earth series from La to Lu and X = CI, Br or I) by an analysis of data on the static and dynamic structure of their molecular monomers. The potential energy function that we adopt is patterned after earlier work on Aluminium trichloride [Z. Akdeniz and M. P. Tosi, Z. Naturforsch. 54a, 180 (1999)], but includes as an essential element the electric polarizability of the trivalent metal ion to account for a pyramidal shape of RX3 molecules. From data referring mostly to trihalides of elements at the ends and in the middle of the rare-earth series (/. e. LaX3, GdX3 and LuX3), we propose systematic variations for the effective valence, ionic radius and electric polarizability of the metal ions across the series. As a first application of our results we predict the structure of the Dy2Cl6 and Dy2Br6 molecular dimers and demonstrate by comparison with electron diffraction data that lanthanide-ion polarizability plays a quantitative role also in this state of tetrahedral-like coordination.

C-Terminal amino acid sequence of chicken pepsinogen and its homology with sequences of other acid proteases

1980 ◽  
Vol 45 (4) ◽  
pp. 1144-1154 ◽  
Author(s):  
Miroslav Baudyš ◽  
Helena Keilová ◽  
Vladimír Kostka
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
The Other ◽  
Terminal Sequence ◽  
Terminal Part ◽  
Terminal Amino Acid ◽  
Tryptic Peptides ◽  
Terminal Amino ◽  
High Degree ◽  
Terminal Amino Acid Sequence

To determine the primary structure of the C-terminal part of the molecule of chicken pepsinogen the tryptic, chymotryptic and thermolytic digest of the protein were investigated and peptides derived from this region were sought. These peptides permitted the following 21-residue C-terminal sequence to be determined: ...Ile-Arg-Glu-Tyr-Tyr-Val-Ile-Phe-Asp-Arg-Ala-Asn-Asn-Lys-Val-Gly-Leu-Ser-Pro-Leu-Ser.COOH. A comparison of this structure with the C-terminal sequential regions of the other acid proteases shows a high degree of homology between chicken pepsinogen and these proteases (e.g., the degree of homology with respect to hog pepsinogen and calf prochymosin is about 66%). Additional tryptic peptides, derived from the N-terminal part of the zymogen molecule whose amino acid sequence has been reported before, were also obtained in this study. This sequence was extended by two residues using an overlapping peptide. An ancillary result of this study was the isolation of tryptic peptides derived from other regions of the zymogen molecule.

Static and Dynamic Structure of Molecular Monomers and Dimers of the Rare-earth Fluorides

2001 ◽  
Vol 56 (5) ◽  
pp. 381-385
Author(s):  
Z. Akdeniz ◽  
M . Gaune-Escard ◽  
M. P. Tosi
Keyword(s):  
Rare Earth ◽  
Bond Length ◽  
Geometrical Structure ◽  
Vibrational Mode ◽  
Dynamic Structure ◽  
Molecular Shape ◽  
Proposed Model ◽  
Infrared Studies ◽  
Charged Clusters ◽  
Good Agreement

Abstract We determine a model of the ionic interactions in RF3 compounds, where R is a rare-earth element in the series from La to Lu, by an analysis of data on the bond length and the vibrational mode frequencies of the PrF3, GdF3 and HoF3 molecular monomers. All RF3 monomers are predicted to have a pyramidal shape, displaying a progressive flattening of the molecular shape in parallel with the lanthanide contraction of the bond length. The vibrational frequencies of all monomers are calculated, the results being in good agreement with the data from infrared studies of matrix-isolated molecules. We also evaluate the geometrical structure and the vibrational spectrum of the La2F6 and Ce2F6 dimers, as a further test of the proposed model. -PACS 36.40.Wa (Charged clusters)

scholarly journals Involvement of loop 5 lysine residues and the N-terminal β-hairpin of the ribotoxin hirsutellin A on its insecticidal activity

2016 ◽  
Vol 397 (2) ◽  
pp. 135-145 ◽  
Author(s):  
Miriam Olombrada ◽  
Lucía García-Ortega ◽  
Javier Lacadena ◽  
Mercedes Oñaderra ◽  
José G. Gavilanes ◽  
...  
Keyword(s):  
Active Sites ◽  
Structural Changes ◽  
The Other ◽  
Spatial Proximity ◽  
Ribonucleolytic Activity ◽  
The Family ◽  
Lysine Residues ◽  
Hirsutella Thompsonii ◽  
Close Spatial Proximity ◽  
High Degree

Abstract Ribotoxins are cytotoxic members of the family of fungal extracellular ribonucleases best represented by RNase T1. They share a high degree of sequence identity and a common structural fold, including the geometric arrangement of their active sites. However, ribotoxins are larger, with a well-defined N-terminal β-hairpin, and display longer and positively charged unstructured loops. These structural differences account for their cytotoxic properties. Unexpectedly, the discovery of hirsutellin A (HtA), a ribotoxin produced by the invertebrate pathogen Hirsutella thompsonii, showed how it was possible to accommodate these features into a shorter amino acid sequence. Examination of HtA N-terminal β-hairpin reveals differences in terms of length, charge, and spatial distribution. Consequently, four different HtA mutants were prepared and characterized. One of them was the result of deleting this hairpin [Δ(8-15)] while the other three affected single Lys residues in its close spatial proximity (K115E, K118E, and K123E). The results obtained support the general conclusion that HtA active site would show a high degree of plasticity, being able to accommodate electrostatic and structural changes not suitable for the other previously known larger ribotoxins, as the variants described here only presented small differences in terms of ribonucleolytic activity and cytotoxicity against cultured insect cells.

Methylene. III. Gas phase reactions with 1-chloropropane

1969 ◽  
Vol 312 (1509) ◽  
pp. 141-161 ◽  
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
The Other ◽  
Gas Phase Reactions ◽  
Other Hand ◽  
Chlorine Substituent ◽  
High Degree ◽  
Singlet Methylene

The work described in this and the following paper is a continuation of that in parts I and II, devoted to elucidation of the mechanism of the reactions of methylene with chloroalkanes, with particular reference to the reactivities of singlet and triplet methylene in abstraction and insertion processes. The products of the reaction between methylene, prepared by the photolysis of ketene, and 1-chloropropane have been identified and estimated and their dependence on reactant pressures, photolysing wavelength and presence of foreign gases (oxygen and carbon mon­oxide) has been investigated. Both insertion and abstraction mechanisms contribute significantly to the over-all reaction, insertion being relatively much more important than with chloroethane. This type of process appears to be confined to singlet methylene. If, as seems likely, there is no insertion into C—Cl bonds under our conditions (see part IV), insertion into C2—H and C3—H bonds occurs in statistical ratio, approximately. On the other hand, the chlorine substituent reduces the probability of insertion into C—H bonds in its vicinity. As in the chloroethane system, both species of methylene show a high degree of selectivity in their abstraction reactions. We find that k S Cl / k S H >7.7, k T Cl / k T H < 0.14, where the k ’s are rate constants for abstraction, and the super- and subscripts indicate the species of methylene and the type of atom abstracted, respectively. Triplet methylene is discriminating in hydrogen abstraction from 1-C 3 H 7 Cl, the overall rates for atoms attached to C1, C2, C3 being in the ratios 2.63:1:0.

The In Vitro Sensitivities of 70 Strains of Shigella

PEDIATRICS ◽  
1964 ◽  
Vol 34 (5) ◽  
pp. 705-707
Author(s):  
WILLIAM D. DONALD
Keyword(s):  
Clinical Trials ◽  
Gastrointestinal Tract ◽  
Tetracycline Resistance ◽  
The Other ◽  
Drug Of Choice ◽  
High Degree ◽  
As Toxicity ◽  
Selection Of

In vitro sensitivities of 70 shigella strains isolated over a recent 18-month period are reported. The high degree of sulfadiazine resistance casts some doubt on the selection of this agent as the drug of choice in the treatment of shigellosis, at least in this community. Some of the other agents, although inhibiting the growth of the organisms in vitro, have disadvantages such as toxicity or failure of absorption from the gastrointestinal tract. Tetracycline resistance was found in only 7% of the organisms tested, but from this and other reports we may anticipate the occurrence of more organisms resistant to this agent. The results of the sensitivities to ampicillin are encouraging and further studies including clinical trials of this agent are in order.

Photoreceptor coupling in turtle retina

1998 ◽  
Vol 15 (4) ◽  
pp. 755-764 ◽  
Author(s):  
M.L. FIRSOV ◽  
D.G. GREEN
Keyword(s):  
Receptive Field ◽  
Gap Junctions ◽  
Direct Evidence ◽  
Physiological Responses ◽  
The Other ◽  
Morphological Data ◽  
Chelydra Serpentina ◽  
Intracellular Injection ◽  
Coupled Cells ◽  
High Degree

Photoreceptors in the isolated turtle retina of two species of turtle, Chelydra serpentina and Pseudemus scripta elegans, were penetrated with double-barrel electrodes. Physiological responses were recorded through one barrel and Neurobiotin tracer was injected from the other. Intracellular injection of Neurobiotin revealed patterns of tracer-coupled photoreceptors. Both the patterns of tracer coupling and the electrophysiology suggest a high degree of specificity of connections. Rods seem to be coupled only to rods and green and red cones seem to be coupled to cones of the same spectral type. Receptive-field profiles, measured with a thin, sharply focused slit of light, often had well-defined peaks and troughs in sensitivity. We have taken advantage of this observation and used the position of a peak in sensitivity to locate the position on the retina of a coupled cell. In one rod, it was possible to correlate physiological and morphological data and to show that the peaks in the physiological receptive field occurred at positions on the retina where there were dye-coupled cells. This provides direct evidence that gap junctions produce the physiological coupling between rods.

scholarly journals Sleep, eat and talk: symbolic enstillment

2021 ◽  
pp. 153-170
Author(s):  
Ruth Ramalho Ruivo Palladino ◽  
Luiz Augusto de Paula Souza ◽  
Mara Lucia Pallotta ◽  
Rogério da Costa ◽  
Maria Claudia Cunha
Keyword(s):  
Child Development ◽  
Dynamic Structure ◽  
The Other ◽  
Biological Functions ◽  
Treatment Procedures ◽  
And Behavior

Sleep, food and language are pillars of children’s healthy lives, are intertwined from birth and make up the dynamic structure of child development. These are the effects of interdependent conditions: organic, psychic and social, which involve the child and result, simultaneously, from organic and symbolic inheritances. The latter overdetermines and modulates the interaction of the child with the environment, especially with the other human who is there. This heritage will draw patterns of conduct and behavior that can often contribute to changes that compromise, to some extent, the overall development of the child. In the children’s clinic, the description of developmentdisorders, from the mildest to the most severe, includes, as a rule, food, sleep and language aspects, which suggests, then, a base triad, questioning clinicians as to the possibility of there being, more than a simple coincidence, a correlation between fundamental biological functions. If this is the case, it will be important for the clinician to appropriate this perspective, since the implication will probably determine particularities in the diagnostic and treatment procedures. In this direction, it is worth deepening and discussing the development of these functions (sleep, diet, language), seeking to clarify their constitutive correlation, the link between them.

scholarly journals Żywiołowe rozprzestrzenianie się Poznania: profil morfologiczny i mikroekonomiczny

2020 ◽  
pp. 81-99
Author(s):  
Piotr Lityński
Keyword(s):  
Spatial Structure ◽  
Urban Sprawl ◽  
The Other ◽  
Moderate Degree ◽  
Financial Situation ◽  
Housing Preferences ◽  
Household Budget ◽  
High Degree ◽  
Financial Losses ◽  
Morphological Assessment

The aim of the article is to assess Poznań’s urban sprawl from the perspective of the morphology of space and financial situation of suburban households. The morphological assessment uses a method based on two grids of squares with a side: 1 km, 500 m; and data on the location of buildings from CCGCD. On the other hand, the assessment of households was carried out on the basis of the CSO Household Budget database. The results of the research indicate that the analyzed communes in the Poznań area are characterized by a moderate degree of disorder in the spatial structure. There are no communes with a completely compact specificity, there are also no communes with an absolutely high degree of spatial disorder. Households causing urban sprawl in Poznań are entities that incur moderate financial losses in order to maximize their housing preferences.

scholarly journals Formación y cultura escrita: los libros del agrimensor Francisco Falcón (1764)

2020 ◽  
pp. 611
Author(s):  
Amparo García Cuadrado
Keyword(s):  
Eighteenth Century ◽  
Quantitative Analysis ◽  
The Other ◽  
Interesting Part ◽  
The Subject ◽  
Scientific Nature ◽  
High Degree ◽  
The Relationship ◽  
Private Collections ◽  
Bibliographic Collection

This article approaches the study of the private library of the Murcian land surveyor Francisco Falcón de los Reyes, from the first half of the eighteenth century, which constitutes a clear example of the relationship between education and written culture. From the data extracted from a postmortem inventory and the subsequent appraisal and partition of goods among the heirs, we carried out a quantitative and qualitative analysis of said library. First, the text provides a biographical profile of this geometer, a descendant of slaves (new Christians), and describes the formative precariousness of these professionals in their time. The quantitative analysis of the bibliographic collection and its comparison with other private collections from similar socioeconomic fields indicate the importance of this particular collection. The qualitative study of authors and titles shows, on one hand, the high degree of mathematical training of the subject, who is shown to be a recipient of the fundamentally Valencian pre-illustrated reformist scientific mainstream, and, on the other hand, the purpose with which those books were incorporated into the funds of the collection. Together with the library, which we could call professional, due to its scientific nature, the inventoried religious matter in the form of printed documents makes up another interesting part of the collection, one of a catechetical nature in its various formative levels

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