Isopiestic Determination of the Osmotic and Activity Coefficients of K<Subscript>2</Subscript>HPO<Subscript>4</Subscript>(aq), Including Saturated and Supersaturated Solutions,at <Emphasis Type="Italic">T</Emphasis>=298.15 K

The osmotic coefficients of K₂HPO₄(aq) have been measured at T=298.15 K by the isopiestic vapor pressure method over the range of molalities from 1.3846 mol⋅kg⁻¹ to 13.939 mol⋅kg⁻¹ (oversaturation) with CaCl₂(aq) as the reference solution. The molalities and osmotic coefficients of saturated solutions in equilibrium with K₂HPO₄⋅xH₂O(cr) were measured simultaneously by the same method. Available literature osmotic coefficients of K₂HPO₄(aq) at T=298.15 K, and our new experimental data, were combined and modeled using an extended form of Pitzer’s equation and the Clegg-Pitzer-Brimblecombe equation based on the mole-fraction-composition scale. These equations were used to calculate the activity coefficients of K₂HPO₄(aq) at T=298.15 K.     

Structural identification of SAR-943 metabolites generated by human liver microsomes in vitro using mass spectrometry in combination with analysis of fragmentation patterns

SAR-943 (32-deoxo rapamycin) is a proliferation signal inhibitor via interaction with the mammalian target of rapamycin (mTOR). Most importantly, SAR-943 has improved chemical stability compared to rapamycin (sirolimus) and is currently under investigation as a drug coated on coronary stents. It was the goal of this study to identify the SAR-943 metabolites generated after incubation with human liver microsomes using high-resolution mass spectrometry (MS) and MS/iontrap (MS(n)) and comparison of fragmentation patterns of the metabolites with those of SAR-943 and other known rapamycin derivatives. Our study showed that SAR-943 is mainly hydroxylated and/or demethylated by human liver microsomes. The structures of the following metabolites were identified: O-demethylated metabolites: 39-O-desmethyl, 16-O-desmethyl and 27-O-desmethyl SAR-943; hydroxylated metabolites: hydroxy piperidine SAR-943, 11-hydroxy, 12-hydroxy, 14-hydroxy, 23-hydroxy, 24-hydroxy, 25-hydroxy, 46-hydroxy and 49-hydroxy SAR-943; didemethylated metabolites: 16,39-O-didesmethyl and 27,39-O-didesmethyl SAR-943; demethylated-hydroxylated metabolites: 39-O-desmethyl, 23- or 24-hydroxy and 39-O-desmethyl, hydroxy piperidine SAR-943 and dihydroxylated metabolites: 12-,23- or 24-dihydroxy SAR-943. In addition, several other demethylated-hydroxylated and dihydroxylated metabolites were detected. However, their exact structures could not be identified.     

Comparison of UPLC and HPLC for Analysis of Dietary Folates

Ultra performance liquid chromatography (UPLC) using small sub-2 ??m particles and high performance liquid chromatography (HPLC) were compared for separation and determination of the most common dietary folates; 5-methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolic acid and folic acid. Two UPLC columns??Acquity BEH C₁₈ and Acquity HSS T3, and two HPLC columns with similar surface chemistry??Xbridge C₁₈ and Atlantis d18 were tested. When using UPLC, the signal-to-noise ratio could be improved by a factor of 2?C50 for different folate derivatives and the run time could be reduced fourfold without sacrificing separation efficiency. The applicability of UPLC to real food samples was demonstrated.     

catena‐Poly[[[(di‐2‐pyridylamine‐κ2N2,N2′)copper(II)]‐μ‐benzene‐1,3‐dicarboxylato‐κ3O1,O1′:O3] monohydrate], a zigzag coordination polymer with strong π–π interactions

The novel title coordination polymer, {[Cu(C₈H₄O₄)(C₁₀H₉N₃)]·H₂O}_n, synthesized by the slow‐diffusion method, takes the form of one‐dimensional zigzag chains built up of Cu^II cations linked by benzene‐1,3‐dicarboxylate (ipht) anions. An exceptional characteristic of this structure is that it belongs to a small group of metal–organic polymers where ipht is coordinated as a bridging tridentate ligand with monodentate and chelate coordination of individual carboxylate groups. The Cu^II cation has a highly distorted square‐pyramidal geometry formed by three O atoms from two ipht anions and two N atoms from a di‐2‐pyridylamine (dipya) ligand. The zigzag chains, which run along the b axis, further construct a three‐dimensional metal–organic framework via strong face‐to‐face π–π interactions and hydrogen bonds. A solvent water molecule is linked to the different carboxylate groups via hydrogen bonds. Thermogravimetric and differential scanning calorimetric analyses confirm the strong hydrogen bonding.     

Analysis of a fast method for solving the high frequency Helmholtz equation in one dimension

We propose and analyze a fast method for computing the solution of the high frequency Helmholtz equation in a bounded one-dimensional domain with a variable wave speed function. The method is based on wave splitting. The Helmholtz equation is split into one-way wave equations with source functions which are solved iteratively for a given tolerance. The source functions depend on the wave speed function and on the solutions of the one-way wave equations from the previous iteration. The solution of the Helmholtz equation is then approximated by the sum of the one-way solutions at every iteration. To improve the computational cost, the source functions are thresholded and in the domain where they are equal to zero, the one-way wave equations are solved with geometrical optics with a computational cost independent of the frequency. Elsewhere, the equations are fully resolved with a Runge–Kutta method. We have been able to show rigorously in one dimension that the algorithm is convergent and that for fixed accuracy, the computational cost is asymptotically just O(w^{1/ p})\mathcal {O}(\omega^{1/ p}) for a pth order Runge–Kutta method, where ω is the frequency. Numerical experiments indicate that the growth rate of the computational cost is much slower than a direct method and can be close to the asymptotic rate.     

Small-Angle and Wide-Angle X-Ray Scattering Study of Slow Relaxation Following Phase Transitions of New Bolaamphiphiles Based on N-(12-Betainylamino-Dodecane)-octyl β-D-Glucofuranosiduronamide Chloride

In the present study, we investigated the polymorphism and its time-dependence of a new series of bolaamphiphile molecules based on N-(12-Betainylamino-dodecane)-octyl β-D-Glucofuranosiduronamide Chloride. To obtain six members of this series, the length of the main bridging chain and the lateral chain were varied in order to modify the hydrophilic–lipophilic balance. Another chemical modification was to introduce a diacetylenic unit in the middle of the bridging chain to study the influence of the π–π stacking on the supramolecular organization of these molecules. Dry bolaamphiphiles self-organize in supramolecular structures such as lamellar crystalline structure, L_c; lamellar gel structure, L_β′; lamellar fluid structure, L_α; and lamellar isotropic structure, L. Thermal hysteresis of these structures, following phase transitions, are investigated by small-angle and wide-angle X-ray scattering. Once the thermal cycle is accomplished, the system remains in the kinetically stabilized undercooled high-temperature phase at the temperature of 20°C. Subsequently, the time-dependence of the relaxation to the thermodynamically stable phase is followed, and very slow relaxation for a period on the order of hours or days is observed. The study of the polymorphism and the stability of various phases of this new series of bolaamphiphiles—which are issued from natural primary resources (sugar beet and wheat) and thus interesting for potential application in pharmaceutical, cosmetics, or food industry—was undertaken in this work.     

Electron Probe Microanalysis of HfO2 Thin Films on Conductive and Insulating Substrates

Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO₂ films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al₂O₃, Ta₂O₅ and TiO₂ films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.     

How far, how long: on the temporal scope of prosodic boundary effects

Acoustic lengthening at prosodic boundaries is well explored, and the articulatory bases for this lengthening are becoming better understood. However, the temporal scope of prosodic boundary effects has not been examined in the articulatory domain. The few acoustic studies examining the distribution of lengthening indicate that boundary effects extend from one to three syllables before the boundary, and that effects diminish as distance from the boundary increases. This diminishment is consistent with the pi-gesture model of prosodic influence [Byrd and Saltzman, J. Phonetics 31, 149-180 (2003)]. The present experiment tests the preboundary and postboundary scope of articulatory lengthening at an intonational phrase boundary. Movement-tracking data are used to evaluate durations of consonant closing and opening movements, acceleration durations, and consonant spatial magnitude. Results indicate that prosodic boundary effects exist locally near the phrase boundary in both directions, diminishing in magnitude more remotely for those subjects who exhibit extended effects. Small postboundary effects that are compensatory in direction are also observed.