2,746 research outputs found
Infrared spectra of the products of interaction of tungsten and molybdenum with fluorine isolated in solid argon
No full textThe IR spectra of the products formed when molecular fluorine passed over molybdenum and tungsten (heated to 100-1100 degreesC) and isolated in inert matrices at 12 K were recorded. In the W + F-2 system, the major product was tungsten hexafluoride. For the Mo + F-2 system, bands of MoF6, MoOF4, (MoF5)(3), MoF5, MoF4, and, possibly, MoF3 were identified. The spectra were interpreted with the use of thermodynamic calculations of the equilibrium composition of the gas phase at various temperatures. The structure of metal fluorides of different compositions is discussed
The infrared spectra of products of tantalum and ruthenium reactions with fluorine isolated in solid argon
No full textThe IR spectra of the products formed when molecular fluorine was passed over tantalum and ruthenium heated to 100-1100 degreesC and isolated in inert matrices at 12 K were studied. In the Ta + F-2 system, bands of (TaF5)(3), TaF5, and TaF4 were observed. In the Ru + F-2 system, the major reaction product was monomeric ruthenium pentafluoride. The structures of metal fluorides of various compositions are discussed
EXAFS and optical spectroscopy characterisation of reduction products of binary silver-copper ion mixture in mordenite
No full textAg+, Cu2+ and Ag+-Cu2+ binary mixtures with different Ag/Cu ratios were supported on mordenite with Si/Al ratio equal to 10 and reduced in the temperature range 323-673 K. Diffuse Reflectance UV-Visible spectra reveal appearance of Ag-8 clusters and small copper metal particles. Cu K-edge EXAFS show for Cu-rich non-reduced samples the presence of only oxygen shell; but for the Ag-rich sample, the presence of heavier backscatterer is also indicated producing a different EXAFS envelope. Silver EXAFS analysis suggests that, for the reduced samples, there are both Ag - 0 and Ag - Ag distances (Ag - Ag and Ag - O coordination numbers of approx 2 and of 1.3 respectively for the Ag/Cu = 3:1. and 1:3 samples). Importantly. for the reduced sample, the EXAFS indicates that Ag appears to promote/stabilise Cu cluster formation whereas Cu appears to impede/destabilise Ag cluster formation
Stabilization of molecular complexes of aluminum chloride with water by matrix isolation
No full textTravels in Mesopotamia including a journey from Aleppo to Bagdad, by the route of Beer, Orfah, Diarbekr, Mardin, and Mousul; with researches on the Ruins of Nineveh, Babylon, and other ancient cities. By J.S. Buckingham, author of Travels in Palestine an
No full textPreface: By Buckingham, J.S.Appendix.Dedication: by the author to Lady Hester Lucy StanhopeContent description: TitleIllustration: 14 (Views ,varia ,)Pagination: pp20+479p, pp4+538pVolumes: 2Text Genre:ProseIllustration: 14 (τοπία ,άλλα θέματα ,
EXAFS and optical spectroscopy characterisation of silver within zeolite matrices
No full textThe study of silver-zeolite samples by a combination of EXAFS and Diffuse Reflectance UV-Visible spectroscopy has been utilised to discover the effect of the structural type and Si/Al ratio of zeolite matrix as well as influence of reduction temperature on the size, structure and oxidation of silver species stabilised inside zeolite voids. The preparation of silver-zeolite samples at high temperature using mordenite with medium Bronsted acid strength or at low temperature using mordenite with high acid strength leads to fast oxidation of reduced silver species. After reduction at medium temperatures silver clusters interpreted as Ag-8(0) and Ag-8(delta+) are formed in mordenites with intermediate Bronsted acid strength. The reduction of silver samples at high temperature utilising mordenite with a very small concentration of weak Bronsted acid sites leads to the formation of amorphous Ag particles. Deformation of the eight-atom clusters is more prominent in the erionite cavities, where space is more severely restricted than in mordenite channels. It is proposed that the charged Ag-8(delta+) clusters are more deformed than neutral Ag-8(0) clusters
Synthesis, structures and DFT calculations on alkaline-earth metal azide-crown ether complexes
No full textThe first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional theory (DFT). This has allowed the effects of the crystal lattice to be investigated. A study of the MNterminal metal-azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal-azide bond to be investigated in each case. As in our earlier work on alkali metal azide-crown ether complexes, the bonding in the alkaline-earth complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre, and minimising ligand-ligand repulsions
Thermal decomposition of methyl 2-azidopropionate studied by UV photoelectron spectroscopy and matrix isolation IR spectroscopy: heterocyclic intermediate vs imine formation
No full textMethyl 2-azidopropionate (N3CH3CHCOOCH3, M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N2, CO, CO2, CH3CN, and CH3OH as the final decomposition products. Methyl formate (MF) and CH4 are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N2 elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH3OH, and CH3CN (?EG3 = 260.2 kJ/mol) and another leading to CO2, CH4, and CH3CN (?EG3 = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)—4-Me-5-oxazolidone—can also be formed from M2AP via H transfer from the remote O–CH3 group, together with the N2 elimination (?EG3 = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisione
Usage notes and labelling practicies in J.S. Bandtkie’s dictionary – types, functions and frequency
No full textUsage notes and labelling practicies in J.S. Bandtkie’s dictionary – types,functions and frequency. The present text discusses the issues related to the phenomenon that is enormously important for the study of historical lexicography, namely the issue of usage notes and labelling practices used in dictionaries. The author focuses on the types of stylistic and context markers used in the dictionary compiled by J.S. Bandtkie, their differentiation and estimated frequency of application (frequency of occurrence of given markers against others), and the consistency in the application of specific solutions by the author of the dictionary. Special attention is given to some of the aspects of the use of grammatical information in J.S. Bandtkie’s work and to the consistency in using given
adopted solutions. The article also includes some general remarks on the scientific
merit of the dictionary, one of the most extensive, as far as the lexical resources are concerned, historical dictionaries of the Polish language
Inter institutional workshop on breakwaters
No full text(1) Functional requirements for Breakwaters - Prof. K.d' Angremond (2) Development of fishery harbors in India - Mr. K. Omprakash (3) Non-rubble Breakwaters and optimisation - Prof. K.d' Angremond (4) Wave energy caisson Breakwaters - Dr. S. Neelamani (5) Partially suspended porous wall Breakwaters - Dr. J.S. Mani (6) Case studies on stability of Breakwaters - Prof. V. Sundar (7) Introduction on Ennore coal port project - Mr. L.A. Mayboom (8) Design of Breakwaters for Ennore port - Mr. R. Haggie (9) Construction of Breakwaters for Ennore port - Mr. S. PearsonHydraulic EngineeringCivil Engineering and Geoscience
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