Interaction of nonylphenyl and tributylphenyl ethylene oxide ionic surfactants with highly soluble cyclodextrin derivatives

The modification of the hydrophobicity of some ethoxylated nonylphenol and tributylphenol surfactants with various soluble -cyclodextrin polymers has been studied by reversed-phase chromatography. Stepwise regression analysis proved that the complex forming capacity of surfactants decreases with increasing diameter of the hydrophobic moiety of surfactants, the properties of the crosslinking agent used for preparation of the polymers has no significant effect on the host-guest interaction, the presence of carboxyl groups in the polymer considerably improved the complex stability.     

Imperfect conjugate gradient algorithms for extended quadratic functions

Summary Generalized conjugate gradient algorithms which are invariant to a nonlinear scaling of a strictly convex quadratic function are described. The algorithms when applied to scaled quadratic functionsfR _n R ₁ of the formf(x)=h(F(x)) withF(x) strictly convex quadratic andhC ¹(R ₁) an arbitrary strictly monotone functionh generate the same direction vectors as for the functionF without perfect steps.     

Application of trimethylvinylsilane as a convenient synthetic precursor of (Perfluoroalkyl)ethenes: An unusual fluoride-induced elimination-desilylation coupled reaction

A convenient and effective method for the preparation of perfluoroalkylated ethenes is described. First, the free radical addition of perfluoroalkyl iodides to trimethylvinylsilane in the presence of AIBN gave iodoethylsilane intermediates (F(CF(2))(n)()CH(2)CHISiMe(3), n = 4 (1), 6 (2), 8 (3), 10 (4); 94-99%). Then an unusual dehydrohalogenation-desilylation reaction was effected by tetrabutylammonium fluoride, and finally the product isolation (F(CF(2))(n)()CH=CH(2) (5-8), 62-87%) was facilitated using a fluorous phase separation technique. This novel approach can also be applied to adjust short C(2) hydrocarbon units to functionalized fluorinated segments (e.g., HOCH(2)(CF(2))(8)CH=CH(2) (11), 71%). All structures were verified by state-of-the-art multinuclear one- and two-dimensional NMR experiments involving both homo- ((19)F-(19)F) and heteronuclear ((1)H-(13)C, (19)F-(13)C) correlations based on the GMQFCOPS and inverse (1)H and/or (19)F detected GHSQC, GHMQC sequences with broad-band adiabatic (13)C decoupling.     

Note on asynchronous exponential growth for structured population models

In the present note we show asynchronous exponential growth for important age- and size-structured population models.     

Characterization of californium sources by gamma spectrometry: relevance for nuclear forensics

As part of an experimental validation of a nuclear forensics methodology for Pu source reactor-type discrimination, destructive analysis has been performed on two irradiated UO₂ pellets with different irradiation histories. Analysis has focused on measuring key Sm fission product isotope ratios used in a previously published maximum likelihood methodology to determine the most likely irradiation history of the pellets. A total of 21 Sm isotope ratios were measured within the irradiated pellets, and generally agreed within 20% of the irradiations as simulated using the Monte Carlo Radiation Transport and material depletion code, MCNP6. Results indicate the chosen approach can accurately measure the isotope ratios within 5% experimental error.

     

k-Sets, Convex Quadrilaterals, and the Rectilinear Crossing Number of Kn

We use circular sequences to give an improved lower bound on the minimum number of (≤ k)-sets in a set of points in general position. We then use this to show that if S is a set of n points in general position, then the number □(S) of convex quadrilaterals determined by the points in S is at least 0.37553(ⁿ₄) + O(n³). This in turn implies that the rectilinear crossing number cr(K_n) of the complete graph K_nis at least 0.37553(ⁿ₄) + O(n³), and that Sylvester's Four Point Problem Constant is at least 0.37553. These improved bounds refine results recently obtained by Abrego and Fernandez-Merchant and by Lovasz, Vesztergombi, Wagner, and Welzl.     

Femtosecond pulsed laser deposition of diamond-like carbon films: The effect of double laser pulses

The bonding structure of carbon films prepared by pulsed laser deposition is determined by the plasma properties especially the change of the kinetic energy. Using double laser pulses the ablation process and the characteristics of the generated plasma can be controlled by the setting of the delay between the pulses. In our experiments, amorphous carbon films have been deposited in vacuum onto Si substrates by double pulses from a Ti:sapphire laser (180 fs, λ = 800 nm, at 1 kHz) and a KrF laser system (500 fs, λ = 248 nm, at 5 Hz). The intensities have been varied in the range of 3.4 × 10¹² to 2 × 10¹³ W/cm². The morphology and the main properties of the thin layers were investigated as a function of the time delay between the two ablating pulses (0-116.8 ps) and as a function of the irradiated area on the target surface. Atomic force microscopy, spectroscopic ellipsometry and Raman-spectroscopy were used to characterize the films. It was demonstrated that the change of the delay and the spot size results in the modification of the thickness distribution of the layers, and the carbon sp²/sp³ bonding ratio.     

Structural insights into transient receptor potential vanilloid type 1 (TRPV1) from homology modeling,flexible docking,and mutational studies

The transient receptor potential vanilloid subtype 1 (TRPV1) is a non-selective cation channel composed of four monomers with six transmembrane helices (TM1–TM6). TRPV1 is found in the central and peripheral nervous system, and it is an important therapeutic target for pain relief. We describe here the construction of a tetrameric homology model of rat TRPV1 (rTRPV1). We experimentally evaluated by mutational analysis the contribution of residues of rTRPV1 contributing to ligand binding by the prototypical TRPV1 agonists, capsaicin and resiniferatoxin (RTX). We then performed docking analysis using our homology model. The docking results with capsaicin and RTX showed that our homology model was reliable, affording good agreement with our mutation data. Additionally, the binding mode of a simplified RTX (sRTX) ligand as predicted by the modeling agreed well with those of capsaicin and RTX, accounting for the high binding affinity of the sRTX ligand for TRPV1. Through the homology modeling, docking and mutational studies, we obtained important insights into the ligand-receptor interactions at the molecular level which should prove of value in the design of novel TRPV1 ligands.     

Effect of Phosphate Fertilization on Micronutrient Content of Maize Plant

Abstract

The effect of fertilization and irrigation on phosphate and metal content in maize was studied in an arable land plot experiment on fertilization effects. A field plot experiment was carried out at the Látókép Farm 15 km from Debrecen. Each treatment consisted of 46 m² plots, arranged in a randomized block design with four replication, where the basic treatment was fertilization; the additional treatments were crop rotation, irrigation and cultivation. The soil is Calcareous Chernozem with 2.8–3.0% humus content. The depth of the humus layer is 70–90 cm. The N-content and original P-content of the soil is average, but it is rich in K. Besides macroelements, there is no shortage of trace elements. The element content of maize was determined with a Labtam 8440M inductively coupled plasma atomic emission spectrometer after digestion. A relationship between phosphate and microelement contents in plant was studied. A linear relationship between phosphate and magnesium, and some microelement contents can be found. Linear correlation in P and Mg content of maize was found strongest (Fig 1.).     

Synthesis of biocompatible nanocomposite hydrogels as a local drug delivery system

Nanocomposite biocompatible hydrogels (NCHG) were synthesised as model systems for in situ cured potentially local drug delivery devices for curing periodontal infections. The composite consists of the following components: nanoparticles (NPs), matrix gel, and chlorhexidine (CHX) as antibacterial drug. The NPs were obtained by free radical initiated copolymerization of the monomers, 2-hydroxyethyl methacrylate (HEMA) and polyethyleneglycol dimethacrylate (PEGDMA), in aqueous solution. The same monomers were used to prepare crosslinked matrices by photopolymerization. NCHGs were obtained by mixing NPs, monomers, and drug in an aqueous solution then crosslinked by photopolymerization. Mechanical properties, swelling behavior, and the kinetics of drug release have been investigated. It was found that compression strength values increased with increasing ratio of the crosslinker PEGDMA. Incorporation of NPs into the matrix resulted similar compression strength as the matrix hydrogel. The hydrated NCHGs swelled more slowly but admitted more water. The drug was incorporated in NPs by swelling in CHX aqueous solution or added to the solution of monomer mixture followed by photopolymerization. Studies of release kinetics revealed that on average 60% of the loaded drug was released. The most rapid release was observed over a 24 h period for matrix gels with low crosslinking density. For NCHGs, the release period exceeded 48 h. An unexpected result was observed for NCHGs without drug in the NPs. In this case, increasing release was observed for the first 24 h. Thereafter, however, the apparent quantity of detectable drug decreased dramatically.