Effect of water on the desorption of carbon dioxide from the surface of alumina

Based on investigations of temperature-programmed desorption of CO₂ from -Al₂O₃ surface, three forms of CO₂ adsorption differing considerably in quantitative contributions and temperature ranges of desorption have been distinguished. A significant inhibiting influence of water on CO₂ adsorption has been observed. Water adsorption results in gradual blocking of high and medium-energy adsorptive centers of CO₂ on -Al₂O₃.

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- CO₂ -Al₂O₃ CO₂, . CO₂. CO₂ Al₂O₃ .

     

Vitreous phases of the Ag2O∶B22O3∶P2O5 system

Most optimized vitreous electrolytes are obtained by doping an oxide glass with a salt (MX); the resulting substance has an increased ionic conductivity, but a reduced thermal stability. On the other hand, this paper shows that it is possible to obtain vitreous electrolytes with enhanced electrical and thermal performances by mixing two glass formers. This phenomenon may be called the mixed anion effect. The Ag₂OB₂O₃P₂O₅ system is shown to offer a very interesting example of such a phenomenon.

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Zusammenfassung Optimale glasartige Elektrolyte werden durch Dopen eines Oxydglases mit einem Salz (MX) erhalten; die Produkte weisen eine erhöhte ionische Leitfähigkeit, jedoch auch eine verminderte thermische Stabilität auf. Andererseits wird gezeigt, daß glasartige Elektrolyte mit besseren elektrischen und thermischen Eigenschaften durch Mischen von zwei Glasbildnern erhalten werden können. Für dieses Phänomen wird die Bezeichnung mixed anion effect in Vorschlag gebracht. Es wird gezeigt, daß das System Ag₂OB₂O₃P₂O₅ ein sehr interessantes Beispiel dieses Phänomens bietet.

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MX. , . . . , Ag₂O₂₃₂₅ .

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The NMR data were collected at the Regional NMR Center of the Colorado State University (Fort Collins, Co, USA), funded by NSF Grant CHE-8208821). This research was funded in part by the Italian Department of Education (MPI 40%).     

On the generation mechanism of aromatic cation-radicals under adsorption on zeolites

Nonempirical quantum-chemical calculations suggest a molecular model for oxygen adsorption on Lewis acid sites of zeolites. This adsorption complex is assumed to be capable of acting as an electron acceptor in the generation of benzene cation-radicals.

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. , - .

     

Asymmetric hydrogenation in the presence of polycyclic chiral phosphines, II /8/

The enantiomers of trans-11, 12-bis-(diphenylphosphinomethyl)-9, 10-dihydro-9,10-ethanoanthracene and its perhydrogenated derivative were prepared and used as ligands in the asymmetric hydrogenation of prochiral olefinic substrates. Different selectivities and partiallyhigh optic al yields could be observed

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-11, 12--()-9, 10--9,10- . .

     

Thermogravimetric study of some disperse dyestuffs

Two disperse dyestuffs, though exhibiting similar behaviour upon TG-DTG-DTA, have different dyeing properties. Thermoanalytical investigations are not sufficient to predict dyeing characteristics and fastness.

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Zusammenfassung Zwei Dispersionsfarbstoffe, die sich bei der TG-DTG-DTA ähnlich verhalten, zeigen unterschiedliche Färbeeigenschaften. Thermoanalytische Untersuchungen sind nicht ausreichend, um Färbeeigenschaften und die Farbechteheit vorherzusagen.

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, , , . .

     

Viscosities of solutions of electrolytes and non-electrolytes in ethylene carbonate at 40°C

The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, tetrabutylammonium tetrabutylborate, water, and 3,3-diethylpentane have been measured in the high-dielectric constant solvent, ethylene carbonate (EC) at 40°C. Crude values of the apparent molar volumes of these solutes have also been obtained. Relative viscosities were fitted to the extended Jones-Dole equation, _r=17#x002B;A c ^1/2+B C+D c ².The pattern of the B coefficients is strikingly similar to that previously observed in the high dielectric constant, linear-chain hydrogen-bonded solvent, N-methylacetamide (NMA). Ionic values for _v and B have been obtained using a variety of splitting techniques. Alkali metal ions have large B coefficients indicating strong cation solvation with the normal order Li>Na>K>Cs. Small anions have positive but much smaller B values than in NMA. The observed order does suggest, however, a small degree of anion solvation. Large organic ions do not display the sharp crossing of the Einstein law,D =2.5_v, uniquely characteristic in H₂O of hydrophobic interaction. The two non-electrolytes have negative B coefficients showing that the Einstein law is not valid at the molecular level and that hydrocarbons are not good models for their isoelectronic tetraalkylammonium ion counterparts. An empirical modification of the Einstein law to account for the finite size of the solvent molecules is discussed. As in NMA the D coefficients are roughly linear in the square of B suggesting that they arise from hydrodynamic origins.     

Room-Temperature Mirror Preparation Using Sol-Gel Chemistry and Laminar-Flow Coating Technique

The CEA/DAM megajoule-class pulsed Nd:glass laser devoted to Inertial Confinement Fusion (ICF) research will require 240 cavity-end mirrors. The approved laser design necessitates 42-cm × 46-cm × 9-cm highly-reflective (HR)-coated substrates representing more than 50 m² of coated area. Prototypes of these dielectric mirrors were prepared with interference quaterwave stacks of SiO₂ and ZrO₂-PVP (PolyVinylPyrrolidone) thin films starting from sol-gel colloidal suspensions (sols). Low refractive index material was based on nanosized silica particles and high refractive index coating solution was made of a composite system. The colloidal/polymeric ratio in the composite system has been optimized regarding refractive index value, laser damage threshold and chemical interactions have been studied using FT-IR spectroscopy. A deposition technique so-called Laminar Flow Coating (LFC) has been associated to sol-gel chemistry for HR laser damage-resistant sol-gel coating development. This novel coating method confirmed its main advantages compared to dipping or spinning processes: coating large flat square substrates at room temperature with small solution consumption, good thickness uniformity, weak edge-effects, induced stress-free coating, good optical properties and laser damage resistance fulfilling.     

Investigations in the field of acyl group carriers

Conclusions Two representatives of phosphate ester derivatives of pantothenonitrile have been obtained: the methyl ester of D-(+)-4-C-[2-O-mesylpantothenonitrilyloxy(phenoxy)phosphonyl]-N-benzyloxycarbonylserine and the ethyl ester of D-(+)-4-C-[2-O-mesylpantothenonitrilyl(phenoxy)phosphonyl]-N-benzyloxycarbonylserylglycine.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 3, pp. 174–176, 1969     

Steroids of the spirostan and furostan series from nolina microcarpa III. Structure of nolinofurosides G and H

Two new glycosides which have been called nolinofurosides G(I) and H(III), have been isolated from the leaves ofNolina microcarpa. Nolinofuroside G is the sodium salt of 26--D-glucofuranosyloxy-(25S)-furost-5,20(22)-diene-1, 3-diol 1-sulfate, and nolinofuroside H is the sodium salt of 1--D-fucopyranosyloxy-26--D-glucopyranosyloxy-(25S)-furost-5,20(22)-dinen-1-3-ol 3-sulfate.M. V. Frunze Simferopol' State University. Institute of the Chemistry of Plant Substances, Uzbek. Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 801–806, November–December, 1991.     

Photorefractive Composites Based on Nanocrystalline Carbocyanine Dye J-Aggregates with a Fast Response Time

The use of carbocyanine dye J-aggregates as sensitizers of photoelectric sensitivity and chromophores with the third-order nonlinear optical polarizability made it possible, by the action of two intersecting He–Ne laser (633 nm) beams and an applied electric field, to obtain photorefractive spatial modulation of the refractive index in a nonplasticized polymer layer having the glass transition temperature of about 230°C with a short (20 ms) time of response to this action. A fairly high two-beam-coupling gain coefficient was obtained, which reached a value of = 218 cm^–1 at an applied field of E ₀ = 50 V/m. The net internal gain (difference between the beam-coupling gain coefficient and the absorption coefficient ) was – = 143 cm^–1 under these conditions.     

A Density Functional Study of Ozone and Oxygen Surface Structures on Ni(110)

The dissociative and molecular forms of O₃ adsorbed on nickel were studied by the density functional method (Becke3LYP exchange correlation functional). The energy profile of the ozone decomposition reaction (O₃)_gas (O₃)_ads (O₂)_ads+1/2O₂ on the Ni₁₀ surface cluster was calculated. As opposed to the weakly bound molecular form of oxygen on transition metals, ozone forms a tightly bound surface compound on the surface of nickel. It is attempted to evaluate the heat of oxygen adsorption on the defective surface of Ni using the model of the surface cluster Ni₁₃ with a vacancy . The positions of the surface nickel atoms before and after their interaction with the adsorbate were calculated. It is shown that substantial relaxation of the surface nickel atoms takes place in the course of adsorption. The possibility of stabilization of the molecular ozone-like form of oxygen on the surface of transition metals in conditions of high oxygen coating extent is discussed.     

Sol-Gel Preparation of Silica Films with Controlled Surface Morphology and Their Application to a Low Reflective Glass

Silica coating films with various surface morphologies, such as flat, porous (with deep pores), concave-convex (with hills and valleys), and convex (with hills on flat plane) structure were prepared from a mixture of two kinds of sols derived from polymerized tetraethoxy-silane (TEOS) and methyltriethoxysilane (MTES). Different surface morphologies were obtained by varying the molar ratio r = MTES/TEOS of the coating solution. The surface was flat for r less than 2.5, porous for 2.5 r < 5, concave-convex for 5 r < 7.5, convex for 7.5 r < 13, and again flat for r larger than 13. For 2.5 r < 5, the apparent refractive index of the silica film with porous morphology was decreased to 1.23 by selecting the solvent and by controlling the relative humidity of the coating atmosphere and the heat treatment temperature. Coating of glass with silica films of low refractive index of 1.23 led to the low reflective glasses with visible light reflectance Rvis of less than 0.2%.     

γ-Pyrone derivatives

3, 5-Dibromocomanic acid (3, 5-dibromo- -pyrone -2-carboxylic acid) VI and its ethyl ester, hitherto not described in the literature, are synthesized by the following route: diethyl acetonedioxalate (I) diethyl dibromochelidonate (III) (mono) ethyl dibromochelidonate (IV) diethyl 3, 5-dibromocomanate (V) VI. Direct bromination of diethyl bromochelidonate gives the ester III. 6-Bromocomenic acid and its ethyl ester are prepared, as well as 2-bromo-3-hydroxy - -pyrone. Bromocomanic acid (x-bromo--pyrone-2-carboxylic acid) XVI is synthesized by the following route: I (mono) ethyl chelidonate ethyl comanate comanic acid XVI. Oxonium salts are obtained: acid sulfates of comanic acid and ethyl comanate.For Part VII [1].     

A general route for the synthesis of pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine derivatives

Summary A facile synthesis of 8-substituted pyrimido[4,5:4,5]thieno[2,3-c]pyridazines (6a–i) has been accomplished. The sequence involves the ring closure of a heterocyclic aminonitrile precursor (3) after reaction with (dichloromethylene)-dimethylammonium chloride.

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Eine allgemeine Synthese von Pyrimido[4,5:4,5]thieno[2,3-c]pyridazin-Derivaten

Zusammenfassung Es wurde ein einfacher Syntheseweg für 8-substituierte Pyrimido[4,5:4,5]thieno-[2,3-c]pyridazine entwickelt. Die Reaktion verläuft über den Ringschluß eines heterocyclischen Aminonitrilvorläufers (3) nach Umsetzung mit Dichlormethylen-dimethylammoniumchlorid.

     

Laser Sintering of SnO2 : Sb Sol-Gel Coatings

Sb doped sol-gel SnO2 single layers (thickness 100 nm) were prepared from alcoholic solution and deposited via a dip coating process on fused silica substrates. The coatings have been sintered at a typical rate of 10–15 cm2/s by CO2 laser irradiation. The laser spot was scanned in one direction at a speed of 15,000 cm/s and the sample was moved in a perpendicular one at a speed up to 250 mm/s. The temperature of the topmost 10 m layer was monitored by a fast pyrometer (s resolution). The following properties of the coatings have been determined: the electrical resistivity , the carrier density n, and mobility , the structure, the thickness, the mesoscopic and micromorphology and the density. The sintering by CO2 laser radiation is mainly a thermal driven process. At T 500°C it allows to obtain coatings with a smaller resistivity (6.8×10–3 cm) than those produced by conventional furnace firing (el2.9×10–2 cm). The results are discussed in terms of particle size and packing density.     

Thermal desorption analysis:

Experiments on water desorption from silicate glass powders of different chemical compositions were carried out by means of DSC. In order to establish the desorption energy distributions, a model of the heterogeneous surface was applied to the thermoanalytical desorption curves, and the results are discussed together with contact angle measurements on flat polished glass samples.The maxima in the desorption curves shift to lower temperature with increasing hydrophobic character; this is caused by divalent cations such as Pb²⁺, Ca²⁺ and Zn²⁺, while alkali metal ions are responsible for an increase in the hydrophilic behaviour.

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Zusammenfassung Wasserdesorptionsexperimente an Silikatglaspulvern unterschiedlicher Zusammensetzung wurden mittels DSC ausgeführt. Für die Berechnung von Desorptionsenergieverteilungen wurde ein Modell der heterogenen Oberfläche genutzt und zusammen mit Randwinkelmessungen an glatten, polierten Glasoberflächen diskutiert. Das Maximum der Desorptionskurven verschiebt sich mit wachsendem hydrophoben Verhalten nach tieferen Temperaturen, wofür divalente Kationen wie Pb²⁺ Ca²⁺ Zn²⁺ verantwortlich sind, während Alkaliionen das hydrophile Verhalten begünstigen.

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. . , , , .

     

Exciton Chirality. (A) Origins of and (B) Applications from Strongly Fluorescent Dipyrrinone Chromophores

(A) The origin of exciton interaction and examples of its application to organic stereochemistry are presented. (B) N,N-Carbonyl-bridged dipyrrinones constitute a new class of highly fluorescent chromophores suitable for investigations of stereochemistry and absolute configuration. N,N-Carbonylxanthobilirubic acid esters are strongly fluorescent, with a fluorescence quantum yield (_F) 0.8, but produce only weak exciton CD from the trans-1,2-cyclohexanediol template. The ester of an analog with benzoic acid replacing propionic, N,N-carbonyl-8-(4-carboxyphenyl)-3-ethyl-2,7,9-trimethyl-(10H)-dipyrrin-1-one, exhibits strong fluorescence (_F=0.68, _em=493nm, _ex=422nm in CHCl₃) and UV-Vis absorption (21000 at 424nm) in organic solvents. Its diester with (1S,2S)-cyclohexanediol is fluorescent and exhibits exciton circular dichroism (=+15dm³·mol^–1·cm^–1, =432nm; =–4dm³·mol^–1cm^–1, =380nm) that correlates with the Exciton Chirality Rule.     

Structure of karatavicin

Summary The synthesis of the following 1, 4-diphosphoinositides has been effected: the - (, -distearoyl) glyceryl ester of myoinositol 1, 4-diphosphate (VI) or (VII) and 1, 4-bis-[ - (, -distearoyl) glycerylphosphoryl] myoinositol (VIII).Khimiya Prirodnykh Soedinenii, Vol. 2, No. 4, pp. 230–233, 1966     

Fast protein separation and characterization by hydrophobic interaction chromatography (HIC) and low angle laser light scattering photometry (LALLS)

Summary Fast gradient HIC has been interfaced with low angle laser light scattering photometry (LALLS) to separate and characterize proteins. Molecular weights (MWs) have been determined on-line for a set of four proteins. A fast HIC column has been used to elute proteins under fast (5 min) and conventional (10 min) gradients. Certain variables used in the calculation of MW, such as refractive index of the mobile phase (RI) and differential refractive index (dn/dc) have been calculated offline.The MWs for three of the four proteins studied matched literature values at any given gradient time. One of the proteins, -lactoglobulin-A (-LACT), was a dimer when injected. Our results have indicated that fast gradient HIC can be easily interfaced with LALLS in spite of a significant change in RI across the gradient.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.