Diluent effects on the Debye-type dielectric relaxation in viscous monohydroxy alcohols

With the recognition that the Debye-type dielectric relaxation of liquid monohydroxy alcohols does not reflect the structural relaxation dynamics associated with the viscous flow and the glass transition, its behavior upon dilution is expected to differ from that of real alpha-processes. We have investigated the Debye-type dielectric relaxation of binary alcohol/alkane mixtures across the entire concentration range in the supercooled regimes. The focus is on 2-ethyl-1-hexanol in two nonpolar liquids, 3-methylpentane and squalane, which are more fluid and more viscous than the alcohol, respectively. The Debye relaxation is found to occur only for alcohol mole fractions x > 0.2 and is always accompanied by a non-Debye relaxation originating from the alcohol component. Prior to its complete disappearance, the Debye relaxation is subject to broadening. We observe that the Debye dynamics of 2-ethyl-1-hexanol is accelerated in the more fluid 3-methylpentane, while the more viscous squalane leads to longer Debye relaxation times. The present experiments also provide evidence that the breakdown of the Debye relaxation amplitude does not imply the absence of hydrogen-bonded structures.     

Silver,iron, and nickel immobilized on hydroxyapatite‐core‐shell γ‐Fe2O3 MNPs catalyzed one‐pot five‐component reactions for the synthesis of tetrahydropyridines by tandem condensation of amines,aldehydes, and methyl acetoacetate

In this study, Ag, Ni²⁺, and Fe²⁺ immobilized on hydroxyapatite‐core‐shell γ‐Fe₂O₃ nanoparticles (γ‐Fe₂O₃@HAp‐Ag, γ‐Fe₂O₃@HAp‐Ni²⁺, and γ‐Fe₂O₃@HAp‐Fe²⁺) as a new and reusable Lewis acid magnetic nanocatalyst was successfully synthesized and reported for an atom economic, extremely facile, and environmentally benign procedure for the synthesis of highly functionalized tetrahydropyridines derivatives 4a‐t is described by one‐pot five‐component reaction of 2 equiv of aldehydes 1 , 2 equiv of amines 2 , and 1 equiv of methyl acetoacetate 3 in EtOH at room temperature in good to high yields and short reaction time. The presented methodology offers several advantages such as easy work‐up procedure, reusability of the magnetic nanocatalyst, operational simplicity, green synthesis avoiding toxic reagents and solvent, mild reaction conditions, and no tedious column chromatographic separation.     

Biosynthesis of gold nanoparticles using Allium noeanum Reut. ex Regel leaves aqueous extract; characterization and analysis of their cytotoxicity,antioxidant, and antibacterial properties

Gold nanoparticles have unique and excellent medical and nonmedical properties and application compared with other metallic nanoparticles. Recently, they have been used for the prevention, control, and treatment of bacterial and fungal diseases. In the recent study, fresh and clean leaves of Allium noeanum Reut. ex Regel leaves have been used for the synthesis of gold nanoparticles. Also, we evaluated the cytotoxicity, antioxidant, and antibacterial properties of HAuCl₄, A. noeanum, and the synthesized nanoparticles (Au NPs). These nanoparticles were analyzed by FT‐IR, UV, XRD, EDS, FE‐SEM, and TEM tests. FTIR results offered antioxidant compounds in the plant were the sources of reducing power, reducing gold ions to Au NPs. In TEM images revealed an average diameter of 10‐30 nm. At the beginning of biological experiments, DPPH free radical scavenging test was carried out to examine the antioxidant property. Also, in the bacterial part of this study, the concentration of HAuCl₄, A. noeanum, and AuNPs with minimum dilution and no turbidity was considered MIC. To determine MBC, 60 μL of MIC and three preceding chambers were cultured on Muller Hinton Agar. The minimum concentration with no bacterial growth was considered MBC. Au NPs revealed excellent antioxidant potential against DPPH, non‐toxicity property against human umbilical vein endothelial cells, and antibacterial activities against Streptococcus pneumonia, Bacillus subtilis, Staphylococcus aureus, Staphylococcus saprophyticus, Salmonella typhimurium, Pseudomonas aeruginosa, Shigella flexneri, and Escherichia coli O157:H7. These findings show that the inclusion of A. noeanum extract improves the solubility of Au NPs, which led to a notable enhancement in the antioxidant and antibacterial effects.     

Uniqueness for inverse Sturm–Liouville problems with a finite number of transmission conditions

We establish various uniqueness results for inverse spectral problems of Sturm–Liouville operators with a finite number of discontinuities at interior points at which we impose the usual transmission conditions. We consider both the cases of classical Robin and of eigenparameter dependent boundary conditions.     

Diamond-Free Subsets in the Linear Lattices

Four distinct elements a, b, c, and d of a poset form a diamond if \(a< b and \(a . A subset of a poset is diamond-free if no four elements of the subset form a diamond. Even in the Boolean lattices, finding the size of the largest diamond-free subset remains an open problem. In this paper, we consider the linear lattices—poset of subspaces of a finite dimensional vector space over a finite field of order q—and extend the results of Griggs et al. (J. Combin. Theory Ser. A 119(2):310–322, 2012) on the Boolean lattices, to prove that the number of elements of a diamond-free subset of a linear lattice can be no larger than \(2+\frac {1}{q+1}\) times the width of the lattice, so that this fraction tends to 2 as \(q \longrightarrow \infty \) . In addition, using an algebraic technique, we introduce so-called diamond matchings, and prove that for linear lattices of dimensions up to 5, the size of a largest diamond-free subset is equal to the sum of the largest two rank numbers of the lattice.     

Edge-shared [M2Cl10]2? complexes of reaction between oxophilic group 4 metal and phosphorus ylides

The reactions between oxophilic group 4 metal chlorides, ??-keto ylides in THF, led to the formation of titanium, zirconium and hafnium edge-shared [M₂Cl₁₀]^2? complexes (1a?C3f). We describe that the reaction between MCl₄ (M = Ti, Zr and Hf) with phosphorus ylides produce edge-shared [M₂X₁₀]^2? complexes instead of O-coordination previously reported complexes. Adding dimethyl sulfoxide (DMSO) to these complexes in room temperature crystalline solid [M(DMSO)₈] · 4Cl · mH₂O · DMSO] (M = Ti (1g), Zr (2g) and Hf (3g); m = 0?C3) together with phosphonium salts in mother liquid were formed. The compounds were characterized by elemental analysis, IR and ¹H, ¹³C and ³¹P NMR spectroscopy.     

Dynamics of glass-forming liquids. VIII. Dielectric signature of probe rotation and bulk dynamics in branched alkanes

We have measured the dielectric relaxation of several glass forming branched alkanes with very low dielectric loss in the frequency range 50 Hz-20 kHz. The molecular liquids of this study are 3-methylpentane, 3-methylheptane, 4-methylheptane, 2,3-dimethylpentane, and 2,4,6-trimethylheptane. All liquids display asymmetric loss peaks typical of supercooled liquids and slow beta relaxations of similar amplitudes. As an unusual feature, deliberate doping with 2-ethyl-1-hexanol, 5-methyl-2-hexanol, 2-methyl-1-butanol, 1-propanol, or 2-methyltetrahydrofuran at the 1 wt % level generates additional relaxation peaks at frequencies below those of the alpha relaxation. The relaxation times of these sub-alpha-peaks increase systematically with the size of the dopant molecules. Because these features are spectrally separate from the bulk dynamics, the rotational behavior and effective dipole moments of the probes can be studied in detail. For the alcohol guest molecules, the large relative rotational time scales and small effective dipole moments are indicative of hydrogen bonded clusters instead of individual molecules.     

Unique factorization in generalized power series rings

Let be a field of characteristic zero and let denote the ring of generalized power series (i.e., formal sums with well-ordered support) with coefficients in , and non-positive real exponents. Berarducci (2000) constructed an irreducible omnific integer, in the sense of Conway (2001), by first proving that an element of that is not divisible by a monomial and whose support has order type (or for some ordinal ) must be irreducible. In this paper, we consider elements of with support of order type . The irreducibility of these elements cannot be deduced solely from the order type of their support and, after developing new tools for studying these elements, we exhibit both reducible and irreducible elements of this type. We further prove that all elements whose support has order type and which are not divisible by a monomial factor uniquely into irreducibles. This provides, in the ring , a class of reducible elements for which we have unique factorization into irreducibles.

     

A Spectroscopic Study of the Effects of Various Solvents and Sol-Gel Hosts on the Chemical and Photochemical Properties of Thionin and Nile Blue A

Tetraethyl orthosilicate (TEOS)-based gels were doped with two optically active organic indicators, thionin and nile blue A. Before trapping in a sol-gel host, thionin and nile blue A were both evaluated for solvent and protonation effects on their spectral properties. Only extreme pH values provided by HCl, NaOH, and NH₄OH produced new absorption and/or fluorescence bands. Introduction of nile blue A into alkaline environments (0.1N NaOH, NH₄OH) results in the appearance of a broad absorption band centered near 520 nm whereas highly acidic environments (1N HCl) show a reduction of the 635 nm absorption peak accompanied by an absorption band located near 460 nm. A marked decrease is observed in the optical density of thionin in 1N HCl solution which results in a reduction in the fluorescence intensity. The absorption and fluorescence spectra also reveal a decrease in a pH 11 solution of NH₄OH as compared to neutral conditions. Both dyes formed dimers when the sol-gel host, initially synthesized with TEOS, was organically modified with methyltrimethoxysilane (MTMS). However, thionin dimers were present in all silica-based sol-gel compositions, as evidenced by the absorption and fluorescence spectra. Substitution of MTMS for some of the TEOS in the gel matrix resulted in blue shifts in the absorption and fluorescence spectra of nile blue A. The absorption peak shifted 50 nm to 596 nm whereas the fluorescence shifted around 40 nm to 635 nm. These blue shifts resulted from the reduced polarity of the silica-based xerogel. Thionin also exhibited shifts in its absorption and fluorescence spectra with organic modification by MTMS. The absorption shifted approximately 3 nm to 595 nm while the fluorescence maximum decreased 7 nm to 630 nm. The blue shifts in the spectra of thionin with additions of MTMS were attributed to surface sites that altered the molecular structure of the adsorbed thionin molecules.