Surface segregation of dissolved salt ions

Surface segregation of iodide, but not of fluoride or cesium ions, is observed by a combination of metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS(HeI)) of amorphous solid water exposed to CsI or CsF vapor. The same surface ionic behavior is also derived from molecular dynamics (MD) simulations of the corresponding aqueous salt solutions. The MIES results show the propensity of iodide, but not fluoride, for the surface of the amorphous solid water film, providing thus strong evidence for the suggested presence of heavier halides (iodide, bromide, and to a lesser extent chloride) at the topmost layer of aqueous surfaces. In contrast, no appreciable surface segregation of ions is observed in methanol, neither in the experiment nor in the simulation. Furthermore, the present results indicate that, as far as the thermodynamic aspects of solvation of alkali halides are concerned, amorphous solid water and methanol surfaces behave similarly as surfaces of the corresponding liquids.     

Contribution of tilt boundaries to the total energy spectrum of grain boundaries in polycrystals

By measuring temperatures T _w for the transition from the incomplete to complete wetting of grain boundaries in poly- and bicrystals, the width of the spectrum of tilt grain boundaries and their contribution to the total energy spectrum of grain boundaries in polycrystals have been experimentally estimated. It has been shown that the tilt grain boundaries correspond to a rather narrow (only 5–10%) portion in the total energy spectrum of grain boundaries in polycrystals. In metals with a low stacking fault energy (copper, tin, zinc), the tilt grain boundaries belong to 10–20% of the grain boundaries with the highest transition temperatures T _w (hence, with low energies). In a metal with a high stacking fault energy (aluminum), the values of T _w for the tilt grain boundaries lie nearly in the middle between the minimum (T _w,min) and maximum (T _w,max) transition temperatures from the incomplete to complete wetting of grain boundaries. This means that grain boundaries with the structure corresponding to a lower energy than that of the symmetric twin boundaries (or stacking faults) can exist in aluminum.     

Thermal expansion of Sn2P2S6 crystals

We present the results for thermal expansion coefficients of Sn₂P₂S₆ crystals determined both in the crystallographic system and the system based on eigenvectors of thermal expansion tensor. Peculiarities of temperature evolution of the indicative surface of thermal expansion tensor for Sn₂P₂S₆ are discussed, including the region of their ferroelectric phase transition.     

Condensation of fluorine-substituted benzaldehydes with amines and cyclic ketones

Condensation of fluorine-containing benzaldehydes with naphthalen-2-amine or quinolin-6-amine and cyclic ketones (cyclopentanone, cyclohexanone, and 4-methylcyclohexanone) gave new fluorine-containing derivatives of cyclopenta[c]benzo[f]quinoline, benzo[a]phenanthridine, and cyclopenta[a]- and benzo[a]-[4,7]phenanthroline. Intermediate products, 2-[(fluorophenyl)(2-naphthylamino or quinolin-6-ylamino)methylidene] cyclohexanones, dihydrobenzo[f]quinolines, and dihydro-4,7-phenanthrolines, were isolated.     

Spatial hydration maps and dynamics of naphthalene in ambient and supercritical water

The hydration structures and dynamics of naphthalene in aqueous solution are examined using molecular-dynamics simulations. The simulations are performed at several state points along the coexistence curve of water up to the critical point, and above the critical point with the density fixed at 0.3 g/cm(3). Spatial maps of local atomic pair-density are presented which show a detailed picture of the hydration shell around a bicyclic aromatic structure. The self-diffusion coefficient of naphthalene is also calculated. It is shown that water molecules tend to form pi-type complexes with the two aromatic regions of naphthalene, where water acts as the H-bond donor. At ambient conditions, the hydration shell of naphthalene is comprised, on average, of about 39 water molecules. Within this shell, two water molecules can be identified as pi-coordinating, forming close to one H-bond to the aromatic rings. With increasing temperature, the hydration of naphthalene changes dramatically, leading to the disappearance of the pi-coordination near the critical point.     

3-(4-fluorophenyl)-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-4-carbaldehyde in the synthesis of aza-and diazaphenanthrene derivatives

Condensation of 3-(4-fluorophenyl)-1H-pyrazole-4-carbaldehyde with 2-naphthyl-or 6-quinolylamine and CH-acids (acetone, acetophenone, cyclic mono-and β-diketones) provided new derivatives of benzo[f]quinoline, benzo[a]phenanthridine, benzo[a]acridine, and 4,7-phenanthroline. The arising in the course of the reaction [3-(4-fluorophenyl)-1H-pyrazole-4-ylmethylene]-2-naphthyl-(or 6-quinolyl)amines, [3-(4-fluorophenyl)-1H-pyrazole-4-ylmethylene]-1,3-indandione, and octahydro-1,8-xanthenedione derivatives were isolated.     

Oscillatory phenomena at polyvinylpyridine/silica interfaces

Oscillations of the aggregate sizes of SiO₂ particles covered by an adsorbed layer of poly(vinylpyridine) (PVP) at pH 3 with a periodicity of about 15 h were observed using a particle counting technique. The same oscillation was found for the contact angle values of water on the surface of Si wafers (with top silica layer) covered by adsorbed PVP as a function of exposure time in a PVP water solution.     

The quantification of carbon dioxide in humid air and exhaled breath by selected ion flow tube mass spectrometry

The reactions of carbon dioxide, CO₂, with the precursor ions used for selected ion flow tube mass spectrometry, SIFT‐MS, analyses, viz. H₃O⁺, NO⁺ and O, are so slow that the presence of CO₂ in exhaled breath has, until recently, not had to be accounted for in SIFT‐MS analyses of breath. This has, however, to be accounted for in the analysis of acetaldehyde in breath, because an overlap occurs of the monohydrate of protonated acetaldehyde and the weakly bound adduct ion, H₃O⁺CO₂, formed by the slow association reaction of the precursor ion H₃O⁺ with CO₂ molecules. The understanding of the kinetics of formation and the loss rates of the relevant ions gained from experimentation using the new generation of more sensitive SIFT‐MS instruments now allows accurate quantification of CO₂ in breath using the level of the H₃O⁺CO₂ adduct ion. However, this is complicated by the rapid reaction of H₃O⁺CO₂ with water vapour molecules, H₂O, that are in abundance in exhaled breath. Thus, a study has been carried out of the formation of this adduct ion by the slow three‐body association reaction of H₃O⁺ with CO₂ and its rapid loss in the two‐body reaction with H₂O molecules. It is seen that the signal level of the H₃O⁺CO₂ adduct ion is sensitively dependent on the humidity (H₂O concentration) of the sample to be analysed and a functional form of this dependence has been obtained. This has resulted in an appropriate extension of the SIFT‐MS software and kinetics library that allows accurate measurement of CO₂ levels in air samples, ranging from very low percentage levels (0.03% typical of tropospheric air) to the 6% level that is about the upper limit in exhaled breath. Thus, the level of CO₂ can be traced through single time exhalation cycles along with that of water vapour, also close to the 6% level, and of trace gas metabolites that are present at only a few parts‐per‐billion. This has added a further dimension to the analysis of major and trace compounds in breath using SIFT‐MS. Copyright © 2009 John Wiley & Sons, Ltd.