The glycosides of the leaves from Isoplexis isabelliana (Webb) Masf

The isolation, characterisation and chemical investigation of the cardiac glycosides of the dried leaves of Isoplexis isabelliana (WEBB ) MASF . are described. 7 glucosides B, D, E, J (monoside), K, M, and 1 (monoside) could be obtained in homogenous form, 3 others were mixtures (“A” = A₁ + A₂, “C” = C₁ + C₂, and “G” = G + K). The substances B (gluco-evatromonoside), D (cheiroside A), E (digitoxigenin-glucosido-6-deoxyglucoside), J (digitoxigenin glucoside), and M (digitalinum verum) could be identified with known substances. The new glycosides are derived from 3 genins: digitoxigenin, uzarigenin, and xysmalogenin, which are directly bound to one of the following sugars: 6-deoxyglucose, 2-O-acetyl-6-deoxy-D -glucose, 2,6-dideoxy-D -arabinohexose (= D -canarose), and 2,6-dideoxy-D -ribohexose (= D -digitoxose), terminated by a glucose unit. –Canarobiose, a new crystalline disaccharide of D -glucose and D -canarose, has also been obtained. –Apart from these cardiac glycosides 3 C₂₁-steroids have been isolated (in addition to the 2 known genins γ-digiprogenin and purpnigenin), and their structures elucidated. The presence of 2 sapogenins has been detected.     

Atom transfer radical polymerization of n‐butyl acrylate catalyzed by CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine

The homogeneous atom transfer radical polymerization (ATRP) of n‐butyl acrylate with CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine as a catalyst and ethyl 2‐bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]₀/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N‐dimethylformamide, and 1‐butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index ～ 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self‐regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n‐butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N‐(n‐hexyl)‐2‐pyridylmethanimine‐based system was proven to be applicable to living block copolymerization and living random copolymerization of n‐butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549–3561, 2002     

Steam pretreatment of acid-sprayed and acid-soaked barley straw for production of ethanol

Barley is an abundant crop in Europe, which makes its straw residues an interesting cellulose source for ethanol production. Steam pretreatment of the straw followed by enzymatic hydrolysis converts the cellulose to fermentable sugars. Prior to pretreatment the material is impregnated with a catalyst, for example, H₂SO₄, to enhance enzymatic digestibility of the pretreated straw. Different impregnation techniques can be applied. In this study, soaking and spraying were investigated and compared at the same pretreatment condition in terms of overall yield of glucose and xylose. The overall yield includes the soluble sugars in the liquid from pretreatment, including soluble oligomers, and monomer sugars obtained in the enzymatic hydrolysis. The yields obtained differed for the impregnation techniques. Acid-soaked barley straw gave the highest overall yield of glucose, regardless of impregnation time (10 or 30 min) or acid concentration (0.2 or 1.0 wt%). For xylose, soaking gave the highest overall yield at 0.2 wt% H₂SO₄. An increase in acid concentration resulted in a decrease in xylose yield for both acid-soaked and acid-sprayed barley straw. Optimization of the pretreatment conditions for acid-sprayed barley straw was performed to obtain yields using spraying that were as high as those with soaking. For acid-sprayed barley straw the optimum pretreatment condition for glucose, 1.0 wt% H₂SO₄ and 220°C for 5 min, gave an overall glucose yield of 92% of theoretical based on the composition of the raw material. Pretreatment with 0.2wt% H₂SO₄ at 190°C for 5 min resulted in the highest overall xylose yield, 67% of theoretical based on the composition of the raw material.     

Subnanosecond multiphonon relaxation of divalent copper impurities in LiTaO3

The temperature dependence of the lifetime of the excited ²T₂ state of the Cu²⁺ ion in a LiTaO₃ crystalline host has been measured with picosecond optical pulses. Its value ranges from 450 psec at 22°K to 10 psec at 423°K. Consistent with this result is the observation of weak fluorescence at 1.75 μm having a low temperature quantum efficiency of ～ 10^?6. The experimental results are in reasonably good agreement with recent theoretical models based on strong coupling of the Cu²⁺ impurities to the host lattice.     

A practical synthesis of [C4] N-benzylpiperazine from [C2] glycine

A high yielding gram-scale synthesis of [¹³C₄] N-benzylpiperazine for use as a convenient and versatile building block in isotope labeling studies of clinical drug candidates is reported.     

On the transition from cellular to wavelike patterns during solutal Marangoni convection

We study characteristic convection patterns emerging during the mass transfer of acetic acid from a glycerol-water layer to a superposed acetone layer by means of experiments and numerical simulations. The patterns form as a result of the stationary Marangoni instability. The initial phase of the pattern evolution is studied using high-resolution simulations. They show hierarchically ordered cellular structures which closely resemble experimental observations. In the later stages presently accessible to the experiments, the cells are locally replaced by relaxation oscillation waves. The emergence of these structures is favored when the experiment is performed in narrow cuvettes.     

Pattern formation and mass transfer under stationary solutal Marangoni instability

According to the seminal theory by Sternling and Scriven [1], solutal Marangoni convection during mass transfer of surface-active solutes may occur as either oscillatory or stationary instability. With strong support of Manuel G. Velarde, a combined initiative of experimental works, in particular to mention those of Linde, Wierschem and coworkers, and theory has enabled a classification of dominant wave types of the oscillatory mode and their interactions. In this way a rather comprehensive understanding of the nonlinear evolution of the oscillatory instability could be achieved. A comparably advanced state-of-the-art with respect to the stationary counterpart seemed to be out of reach a short time ago. Recent developments on both the numerical and experimental side, in combination with assessing an extensive number of older experiments, now allow one to draw a more unified picture. By reviewing these works, we show that three main building blocks exist during the nonlinear evolution: roll cells, relaxation oscillations and relaxation oscillations waves. What is frequently called interfacial turbulence results from the interaction between these partly coexisting basic patterns which may additionally occur in different hierarchy levels. The second focus of this review lies on the practical importance of such convection patterns concerning their influence on mass transfer characteristics. Particular attention is paid here to the interaction between Marangoni and buoyancy effects which frequently complicates the pattern formation even more. To shed more light on these dependencies, new simulations regarding the limiting case of stabilizing density stratification and vanishing buoyancy are incorporated.     

Dynamic nuclear polarization enhancement of protons and vanadium‐51 in the presence of pH‐dependent vanadyl radicals

We report applications of dynamic nuclear polarization to enhance proton and vanadium‐51 polarization of vanadyl sulfate samples doped with TOTAPOL under magic angle spinning conditions. The electron paramagnetic resonance response stemming from the paramagnetic ⁵¹V species was monitored as a function of pH, which can be adjusted to improve the enhancement of the proton polarization. By means of cross‐polarization from the proton bath, ⁵¹V spins could be hyperpolarized. Enhancement factors, build‐up times, and longitudinal relaxation times T₁(¹H) and T₁(⁵¹V) were investigated as a function of pH. Copyright © 2014 John Wiley & Sons, Ltd.     

Red Tomato Products as an Alternative to Reduce Synthetic Dyes in the Food Industry: A Review

Most dyes used in the food industry are synthetic and can be a health hazard. Red tomato may serve as a natural alternative dye to replace synthetic colorants. This study aimed to review the literature on the addition of red tomato products (powder tomato, paste, freeze-dried, tomato peel powder, tomato pomace) to reduce the usage of synthetic dyes in the food industry. Red tomato products have been used as coloring in pasta, bologna, sausages, cookies, crackers, macaroons, hamburgers, breads, muffins, cheeses, and nuggets. The trans-cis isomerization of lycopene by oxidative processes directly affects the color of the pigment. The lycopene contained in tomato has antioxidant activity and could reduce or eliminate other oxidants and/or synthetic preservatives in food. Moreover, tomatoes in foods have high sensory scores, nutritional appeal, and marketing potential. However, its use as a food colorant has been not extensively explored. Therefore, further studies are still required, especially on the stability of carotenoids in tomatoes used in processed foods.