On the Propagation of Weakly Nonlinear Random Dispersive Waves

We study several basic dispersive models with random periodic initial data such that the different Fourier modes are independent random variables. Motivated by the vast physics literature on related topics, we then study how much the Fourier modes of the solution at later times remain decorrelated. Our results are sensitive to the resonances associated with the dispersive relation and to the particular choice of the initial data.     

Synthesis and Characterization of Partially Substituted at Lower Rim Phosphorus Containing Calix(4)arenes

The synthesis and characterization of several new phosphorus-containing partially lower rim substituted derivatives of 5,11,17,23-tetra(t-butyl) calix(4)arene (I) and 5,11,17,23-tetra(t-octyl)calix(4)arene (II), namely 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(diphenylphosphinoyl-oxy) calix(4)arene (IV); 5,11,17,23-tetra(t-butyl)-25-hydroxy-26,27,28-tris(tetramethyldiamido-phosphinoyl-oxy) calix(4)arene (Vb); 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene (VI); 5,11,17,23-tetra (t-octyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene (VII) are reported. The structure of the synthesized calix(4)arene derivatives are identified and confirmed by elemental analysis, IR, ¹H, ¹³C, ³¹P{¹H} NMR spectroscopy and mass spectrometry as and X-ray crystallographic analysis of 5,11,17,23-tetra(t-butyl)-25,27-dihydroxy-26,28-bis(dimethyl-phosphinoyl-methoxy) calix(4)arene VI. According to the NMR spectra, all calix(4)arenes are in cone conformation.     

The Effect of α-, β- and γ-Cyclodextrin on Wheat Dough and Bread Properties

Cyclodextrins (CDs) are cyclic oligosaccharides that have found widespread application in numerous fields. CDs have revealed a number of various health benefits, making them potentially useful food supplements and nutraceuticals. In this study, the impact of α-, β-, and γ-CD at different concentrations (up to 8% of the flour weight) on the wheat dough and bread properties were investigated. The impact on dough properties was assessed by alveograph analysis, and it was found that especially β-CD affected the viscoelastic properties. This behavior correlates well with a direct interaction of the CDs with the proteins of the gluten network. The impact on bread volume and bread staling was also assessed. The bread volume was in general not significantly affected by the addition of up to 4% CD, except for 4% α-CD, which slightly increased the bread volume. Larger concentrations of CDs lead to decreasing bread volumes. Bread staling was investigated by texture analysis and low field nuclear magnetic resonance spectroscopy (LF-NMR) measurements, and no effect of the addition of CDs on the staling was observed. Up to 4% CD can, therefore, be added to wheat bread with only minor effects on the dough and bread properties.     

Acetalization of glycerol using mesoporous MoO3/SiO2 solid acid catalyst

Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO₃/SiO₂ as a solid acid catalyst. A series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%) were prepared by sol–gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively. The sol–gel derived samples were calcined at 500 °C and characterized using various physicochemical characterization techniques. The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO₃ loading and at higher loading of crystalline α-MoO₃ on amorphous silica support. TEM analyses of the materials showed the uniform distribution of MoO₃ nanoparticles on amorphous silica support. Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of α-MoO₃ and polymolybdate species at high Mo loadings. Moreover the Raman spectra of intermediate loading samples also suggest the presence of β-MoO₃. Acetalization of glycerol with benzaldehyde was carried out using series of MoO₃/SiO₂ catalysts with varying MoO₃ loadings (1–20 mol%). Among the series, MoO₃/SiO₂ with 20 mol% MoO₃ loadings was found to be the most active catalyst in acetalization under mild conditions. Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 °C with 60% selectivity for the six-membered acetal using 20% MoO₃/SiO₂. Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals. These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process.     

Synthesis and deprotonation of 2-(pyridyl)phenols and 2-(pyridyl)anilines

2-(2- and 3-Pyridyl)anilines (1, 2), 2,2-dimethyl-N-[2-(2- and 3-pyridyl)phenyl]propanamides (3, 4), and 2-, 3- and 4-(2-methoxyphenyl)pyridines (7-9) are readily synthesized using cross-coupling reactions. Whereas the amines 1, 2 undergo side reactions, the corresponding amides 3, 4 are deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LTMP): the compound 3 at C6' under in situ quenching, and the compound 4 at C4'. When the ether 7 is subjected to the same reagent, lithiation occurs at C6'.     

Synthesis and metallation of 2-(pyridyl)benzoic acids and ethyl 2-(pyridyl)benzoates: a new route to azafluorenones

The ring deprotonation of 2-(2- and 4-pyridyl)benzoic acids using lithium dialkylamides in THF at rt, and the in situ cyclization afforded 4- and 2-azafluorenones, respectively. 1-Azafluorenone was obtained from ethyl 2-(3-pyridyl)benzoate using a similar protocol.     

Comments on selected fundamental aspects of microarray analysis

Microarrays are becoming a ubiquitous tool of research in life sciences. However, the working principles of microarray-based methodologies are often misunderstood or apparently ignored by the researchers who actually perform and interpret experiments. This in turn seems to lead to a common over-expectation regarding the explanatory and/or knowledge-generating power of microarray analyses. In this note we intend to explain basic principles of five (5) major groups of analytical techniques used in studies of microarray data and their interpretation: the principal component analysis (PCA), the independent component analysis (ICA), the t-test, the analysis of variance (ANOVA), and self organizing maps (SOM). We discuss answers to selected practical questions related to the analysis of microarray data. We also take a closer look at the experimental setup and the rules, which have to be observed in order to exploit microarrays efficiently. Finally, we discuss in detail the scope and limitations of microarray-based methods. We emphasize the fact that no amount of statistical analysis can compensate for (or replace) a well thought through experimental setup. We conclude that microarrays are indeed useful tools in life sciences but by no means should they be expected to generate complete answers to complex biological questions. We argue that even well posed questions, formulated within a microarray-specific terminology, cannot be completely answered with the use of microarray analyses alone.     

Characterizing the ZrC(111)/c-ZrO2(111) Hetero-Ceramic Interface: First Principles DFT and Atomistic Thermodynamic Modeling

The mechanical and physical properties of zirconium carbide (ZrC) are limited to its ability to deteriorate in oxidizing environments. Low refractory oxides are typically formed as layers on ZrC surfaces when exposed to the slightest concentrations of oxygen. However, this carbide has a wide range of applications in nuclear reactor lines and nozzle flaps in the aerospace industry, just to name a few. To develop mechanically strong and oxygen-resistant ZrC materials, the need for studying and characterizing the oxidized layers, with emphasis on the interfacial structure between ZrC and the oxidized phases, cannot be understated. In this paper, the ZrC(111)//c-ZrO₂ (111) interface was studied by both finite temperature molecular dynamic simulation and DFT. The interfacial mechanical properties were characterized by the work of adhesion which revealed a Zr|OO|Zr|OO//ZrC(111) interface model as the most stable with an oxygen layer from ZrO₂ being deposited on the ZrC(111) surface. Further structural analysis at the interface showed a crack in the first ZrO₂ layer at the interfacial region. Investigations of the electronic structure using the density of state calculations and Bader charge analysis revealed the interfacial properties as local effects with no significant impacts in the bulk regions of the interface slab.     

Lanthanide luminescence efficiency in eight- and nine-coordinate complexes: Role of the radiative lifetime

The photophysical parameters for the sensitization of metal-centred luminescence are analyzed in two series of complexes with tridentate and hexadentate ligands having N_xO_y chelating units. In particular, the radiative lifetime τ_rad is experimentally estimated for 29 nine-coordinate Eu^III complexes and 10 eight- and nine-coordinate Yb^III complexes. The known dependence of τ_rad on refractive index is substantiated by comparing data for solid-state samples and solutions. Moreover, a clear dependence of τ_rad with the coordination environment is evidenced and in the case of Eu^III, a comparison between τ_rad and the nephelauxetic effect generated by the ligands is attempted. Altogether, this extensive analysis points to the importance of having a handle on τ_rad when designing ligands for highly luminescent lanthanide-containing molecular edifices. This, in turn, should stimulate initiating theoretical considerations to unravel a reliable relationship between τ_rad and the electronic structure of the ligands.