New unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands derived from H8-BINOL for highly efficient Rh-catalyzed enantioselective hydrogenation

A series of new H₈-BINOL-derived unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands have been synthesized and successfully used in Rh-catalyzed asymmetric hydrogenations. The same or higher enantioselectivities (99.9% ee) were achieved in the hydrogenation of dimethyl itaconate and α-dehydroamino acid esters as those obtained with BINOL-derived analogues. However, slightly lower enantioselectivities (99.0% ee) were obtained in the hydrogenation of enamides.     

Feasibility of near-infrared spectroscopy to detect and to quantify adulterants in cow milk.

Cow milk adulteration involves the dilution of milk with a less-expensive component, such as water or whey. Near-infrared spectroscopy (NIRS) was employed to detect the adulterations of milk, non-destructively. Two adulteration types of cow milk with water and whey were prepared, respectively. NIR spectra of milk adulterations and natural milk samples in the region of 1100 - 2500 nm were collected. The classification of milk adulterations and natural milk were conducted by using discriminant partial least squares (DPLS) and soft independent modelling of class analogy (SIMCA) methods. PLS calibration models for the determination of water and whey contents in milk adulteration were also developed, individually. Comparisons of the classification methods, wavelength regions and data pretreatments were investigated, and are reported in this study. This study showed that NIR spectroscopy can be used to detect water or whey adulterants and their contents in milk samples.     

Asymptotic Behavior of the t Expansion

The asymptotic behavior of a system's ground-state energy from the t expansion of Horn and Weinstein has been suggested to have the form E ₁(t)=E ₁+exp(–a _n t+b _n ). In the limit of very large t, this becomes E ₁(t)=E ₁+exp(–a ₁ t+b ₁). A simple analysis shows that the parameters are a ₁=E ₂–E ₁ and b ₁=ln[(E ₂–E ₁)|c ₂|²/|c ₁|²]. Functions are introduced which allow determination of a ₁, b ₁ and lower bounds to E ₁.     

Characterization of non-uniformly charged ion-exchange membranes prepared by plasma-induced graft polymerization

Cation-exchange membranes were prepared by plasma-induced grafting of sulfonated glycidyl methacrylate (GMA) and porous polypropylene (PP) membranes. The chemical and physical structures of the prepared membranes were investigated using Fourier transform infrared spectroscopy (FTIR), field emission-scanning electron microscopy (FESEM) and electron-probe micro-analyzing (EPMA). The membranes were also characterized in terms of their electrochemical properties. A non-uniform distribution of fixed charges across the membrane matrix was detected by EPMA analysis. This non-uniform distribution of the fixed charges is the result of using water as solvent for the monomer which led to a fast reaction on the membrane surface and a slow diffusion of the monomer into the pores of the membrane. The prepared membranes exhibited moderate ion-exchange capacities (2.53–3.30 mmol/g dry membrane) and electrical resistances (0.349–0.589 Ω cm²) and an ion permselectivity comparable to that of the commercial membrane CM-1 (Tokuyama Corp.), while the water content of the membranes was significantly higher than that of the commercial membrane. The higher water content of the membranes is the result of water occupying the pores in the bulk of the support membrane after the dense layers with fixed charges are formed on the membrane surfaces by the grafting reaction. The relatively high ion permselectivity in spite of the high water sorption of the membranes is the result of the high fixed charge density in the layers on the membrane surfaces. Current versus voltage curves and the chronopotentiometric measurements revealed that the sulfonated GMA-g-PP membranes can be operated effectively at high current density.     

Structure and dynamics of hydrated NH(4) (+): an ab initio QM/MM molecular dynamics simulation

A combined ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulation has been performed to investigate solvation structure and dynamics of NH(4) (+) in water. The most interesting region, the sphere includes an ammonium ion and its first hydration shell, was treated at the Hartree-Fock level using DZV basis set, while the rest of the system was described by classical pair potentials. On the basis of detailed QM/MM simulation results, the solvation structure of NH(4) (+) is rather flexible, in which many water molecules are cooperatively involved in the solvation shell of the ion. Of particular interest, the QM/MM results show fast translation and rotation of NH(4) (+) in water. This phenomenon has resulted from multiple coordination, which drives the NH(4) (+) to translate and rotate quite freely within its surrounding water molecules. In addition, a "structure-breaking" behavior of the NH(4) (+) is well reflected by the detailed analysis on the water exchange process and the mean residence times of water molecules surrounding the ion.     

Hydrophobicity modification of woven cotton fabric by hydrophobic fumed silica coating

Water repellency of woven cotton fabric was achieved by coating with the aqueous dispersion containing organosilane agent (HDTMS) and fumed silica. The coating agents were applied using padding method and then followed by batching the coated fabric at the ambient temperature for 24 h to allow the condensation reaction between HDTMS silanol group and fumed silica silanol group, rendering silica particles hydrophobic. An ultrasonicator was employed to prepare the homogenous coating dispersion. The water repellency evaluated by water contact angle determination which showed the contact angle over 110° was obtained with low amount of applied HDTMS of 1 wt%. The effect of fumed silica addition on an increase in fiber surface roughness geometry showed the influential result in improving the water contact angle. From durability to washing test, the hydrophobic coatings evidenced from SEM and ATR/FTIR remained adhering to fiber surface, indicating the durability. After washing, the coating on the fabric with fumed silica addition appeared to be scatter particles which made a contribution to the higher contact angle value when compared to sheet-like layer coating in case of HDTMS coating alone.     

Gas chromatographic/mass spectrometric and microbiological analyses on irradiated chicken

Ionizing radiation is widely used as treatment technique for food preservation. It involves among others reduction of microbial contamination, disinfestations, sprout inhibition and extension of shelf life of food. However, the commercialization of irradiated food requires the availability of reliable methods to identify irradiated foodstuffs. In this paper, we present results on the application to irradiated chicken of this method, based on the detection, in muscle and skin samples, of the peaks of ions 98 Da and 112 Da, in a ratio approximately 4:1, typical of radiation induced 2-dodecylcyclobutanones (2-DCB). Aim of the work was also to study the time stability of the measured parameters in samples irradiated at 3 and 5 kGy, and to verify the efficacy of the treatment from a microbiological point of view. Our results show that, one month after irradiation at 3 kGy, the method is suitable using the skin but not the muscle, while the measured parameters are detectable in both samples irradiated at 5 kGy. The microbial population was substantially reduced even at 3 kGy.     

Quantum pharmacological studies on antimalarial drugs

Summary Linear models for the relation between electronic structure and antimalarial activity of chloroquine drugs have been investigated, based on CNDO/2 molecular orbital calculations. The results indicate that changes in electron density on the atoms N1, N2, C4, C9, and C10 have the strongest influence on the pharmacological activity, so that these atoms can be assumed to form the main active center of these drugs. Correlations improve, if substitution on the nucleus of chloroquine and side chain variations are treated separately. The models found seem to be a useful tool for designing new drugs within the chloroquine series.

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Quantenchemisch-pharmakologische Untersuchungen von Antimalaria-Wirkstoffen

Zusammenfassung Auf der Basis von CNDO/2-Rechnungen wurden lineare Modelle für die Relation zwischen Elektronenverteilung und der Antimalaria-Aktivität von Chlorochinen untersucht. Es zeigte sich, daß Veränderungen in den Elektronendichten der Atome N1, N2, C4, C9 und C10 den stärksten Einfluß auf die pharmakologische Wirkung haben. Es kann somit angenommen werden, daß diese Atome die hauptsächlich aktiven Zentren der Verbindung sind. Die Korrelation wird verbessert, wenn die Substitution am Chlorochin-Kern und Variationen der Seitenketten separat behandelt werden. Die aufgefundenen Modellvorstellungen sollten ein nützliches Werkzeug zur gezielten Synthese neuer Wirkstoffe innerhalb der Chlorochin-Reihe darstellen.

     

Study on grafting of different types of acrylic monomers onto natural rubber by γ-rays

 A comparative study of various acrylic monomers for grafting onto natural rubber was done. The stability of natural rubber latex (NRL) against coagulum with monomer, mechanical properties of grafted rubbers and percent of grafting were investigated. The NRL with monomers, methylacrylate (MA), ethylacrylate (EA) and n-butylacrylate (n-BA), is unstable but it is stable with methyl methacrylate (MMA), n-butyl methacrylate (BMA) and cyclohexyl methacrylate (CHMA). The mechanical properties and degree of grafting attained a maximum at a total radiation dose of 4 kGy. The values of tensile properties of MMA and CHMA grafted rubbers are almost similar, and higher than those of BMA grafted rubbers. On the other hand, the degree of grafting for CHMA is higher than those of MMA and BMA grafted rubbers. The infrared (IR) spectra of monomer grafted natural rubber were also studied.     

Voltammetric detection of organohalides by redox catalysis: improved sensitivity by immobilisation within a cubic phase liquid crystal

Two combined strategies are reported for improving the sensitivity of organohalide detection by redox catalysis. These are, improvement of the second order rate constant (k) for catalytic reduction of the organohalide, and improvement of the rate of substrate diffusion. Values of k are calculated for both alkyl and aryl halides, from slow scan rate cyclic voltammograms in homogeneous solution. It is shown that a Zn(ii) porphyrin exhibits higher catalytic rates than the previously used Co(ii) porphyrin or Co(i) salen. Amperometric and rotating disk electrode studies of electropolymerised films of the Zn(ii) porphyrin, reveal that at optimum thickness, mediator-substrate reaction and substrate diffusion are the rate limiting steps. Hence, immobilisation of the Zn(ii) porphyrin within the more open structure of a cubic phase liquid crystal produces an increase in sensitivity of approx. 10 times, and lowers the limit of detection by one order of magnitude. The optimised sensor responds linearly to seven organohalides in the range 0.1 microM to 1.0 microM with a sensitivity of 6.95 A M(-1) cm(-2). Chronoamperometric experiments with a microdisk electrode show that the rate of charge transport in the cubic phase films (apparent diffusion coefficient, D(E)= 5.65 x 10(-10)+/- 0.11 x 10(-10) cm(2) s(-1)) is faster than in the electropolymerised films (D(E)= 3.64 x 10(-11)+/- 0.02 x 10(-11) cm(2) s(-1)). The variation of D(E) with the concentration of Zn(ii) in the cubic phase suggests that diffusion of charge is predominantly by electron self-exchange, rather than by physical movement.