Trigoxyphins O–T,six new heterodimers from Trigonostemon xyphophylloides

Phytochemical study of the twigs of Trigonostemon xyphophylloides led to the isolation of six new heterodimers, trigoxyphins O (1) and R–T (4–6) comprising of two different degraded diterpenoids, and trigoxyphins P (2) and Q (3) comprising a degraded diterpenoid and a phenylpropanoid, together with a known homodimer, neoboutomannin (7). The structures and relative configurations were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 1–6 were evaluated for their cytotoxicity against four human tumour cell lines by MTT assay.     

Palladium-catalyzed C–S bond formation by using N-amido imidazolium salts as ligands

N-Amido imidazolium salt was employed as a ligand in the palladium-catalyzed cross-coupling reaction of aryl halides and thiols, and showed good activity in the formation of thioether. The best combination for the coupling with aryl bromides was N-amido imidazolium salt 2 and NaHMDS, and that for the coupling with aryl iodides was N-amido imidazolium salt 1 and KO^tBu. The coupling reactions were conducted in the presence of Pd(OAc)₂ (1 mol %) in DMSO at 80 °C for 12 h.     

Understanding the electronic energy transfer pathways in the trimeric and hexameric aggregation state of cyanobacteria phycocyanin within the framework of Förster theory

In the present study, the electronic energy transfer pathways in trimeric and hexameric aggregation state of cyanobacteria C‐phycocyanin (C‐PC) were investigated in term of the Förster theory. The corresponding excited states and transition dipole moments of phycocyanobilins (PCBs) located into C‐PC were examined by model chemistry in gas phase at time‐dependent density functional theory (TDDFT), configuration interaction‐singles (CIS), and Zerner's intermediate neglect of differential overlap (ZINDO) levels, respectively. Then, the long‐range pigment‐protein interactions were approximately taken into account by using polarizable continuum model (PCM) at TDDFT level to estimate the influence of protein environment on the preceding calculated physical quantities. The influence of the short‐range interaction caused by aspartate residue nearby PCBs was examined as well. Only when the protonation of PCBs and its long‐ and short‐range interactions were properly taken into account, the calculated energy transfer rates (1/K) in the framework of Förster model at TDDFT/B3LYP/6‐31+G* level were in good agreement with the experimental results of C‐PC monomer and trimer. Furthermore, the present calculated results suggested that the energy transfer pathway in C‐PC monomer is predominant from β‐155 to β‐84 (1/K = 13.4 ps), however, from α‐84 of one monomer to β‐84 (1/K = 0.3–0.4 ps) in a neighbor monomer in C‐PC trimer. In C‐PC hexamer, an additional energy flow was predicted to be from β‐155 (or α‐84) in top trimer to adjacent β‐155 (or α‐84) (1/K = 0.5–2.7 ps) in bottom trimer. © 2013 Wiley Periodicals, Inc.     

Characterization of Optical Properties in Water-in-Oil Emulsion

There have been few studies on the factors that determine the overall appearance of emulsions. Optical properties are quite important in determining the perceived quality of emulsion-based products. The overall appearance of an emulsion is determined by the way that it interacts with electromagnetic radiation in the visible region of the spectrum, for example, reflection, transmission, adsorption, and scattering. These interactions are principally determined by the characteristics of emulsion droplets (size, concentration, and refractive index). The present study aims at characterizing the optical properties and rheological behaviors of water-in-oil emulsions, especially macroemulsions. There is a decrease in the absorbance spectra as increasing glycerin ratio in aqueous phase because the difference of refractive index between oil phase and aqueous phase decreased, which improved the transparency of water-in-oil emulsion. The absorbance of linear and branched surfactant emulsions were smaller than that of alkyl modified branched surfactant emulsion. Moreover the transparency of emulsions prepared with linear and branched surfactants was much clearer than that of alkyl modified branched surfactant emulsion. The absorbance spectra also showed that low polar oil attributed to the more transparent emulsion, compared with high polar or nonpolar oil. However, these kinds of oils were not helpful to prepare transparent emulsion because the appearance of these emulsions was translucent or opaque, even if polyols in aqueous phase was 30 wt%.     

Core/Shell Structured PCM Nanocapsules Obtained by Resin Fortified Emulsion Process

Phase change material (PCM, octadecane) nanocapsules were successfully prepared by resin fortified emulsion (RFE) polymerization using the alkali soluble resin (ASR) of poly(ethylene‐co‐acrylic acid) (EAA) and poly(styrene‐co‐acrylic acid) (SAA). Stable PCM nanocapsules were obtained by resin fortified emulsion polymerization, which could be attributed to the prevention of Ostwald ripening due to PCM being hydrophobic. Analysis of online FTIR measurements throughout the reaction confirmed that the nanocapsules contained octadecane as a PCM. TEM imaging of the PCM nanocapsules showed spherical and core/shell morphology. The characteristics of PCM nanocapsules can be controlled by process parameters. As a result, the particle size and particle size distribution (i.e., polydispersity index (Dw/Dn)) of the PCM nanocapsules were created by adjusting manufacturing conditions. The PCM nanocapsules exhibited thermal energy storage (～49.8 J/g) and release (～47.9 J/g) behavior.     

Minimum detectable activity, systematic uncertainties, and the ISO 11929 standard

The Currie formulation for minimum detectable activity (MDA) has served for decades as the standard method for estimating radiological detection limits-it is simple and statistically defendable. It does, however, lack a means to account for the effects of systematic uncertainties. In recent years we have seen various efforts to incorporate systematic uncertainties into an MDA framework. Perhaps most notable of these is the recent ISO standard 11929 for the determination of characteristic limits in ionizing radiation measurements. This standard brings a Bayesian perspective to the problem of characteristic limits in radiation measurements that are in many ways both welcome and long overdue. In this paper, however, we note some apparent drawbacks to the ISO 11929 approach. Namely, for small values of the systematic uncertainty the correction it makes to the Currie MDA is negligible, while for large systematic uncertainties the calculated MDA values can become infinite. In between these two extremes, the user has little basis for evaluating the reliability of the result. To address these issues, we consider the problem from a new approach, developing a straightforward phenomenological statistical model of the MDA that treats systematic uncertainties explicitly. We compare predictions from our model with results of the ISO 11929 formulation as well as the traditional Currie approach. Finally, some recommendations for alternative handling of the MDA in the face of significant systematic uncertainties are presented.     

Adsorption kinetics and equilibrium modeling of cesium on copper ferrocyanide

The copper ferrocyanide (CuFC) prepared in this study was characterized using X-ray diffraction and scanning election microscopy. The distribution of particle sizes of the CuFC suspension was determined. The adsorption kinetics data were evaluated for an intraparticle diffusion model, a pseudo-first order model and a pseudo-second order model at temperatures of 288, 298 and 308 K, respectively. It was found that the adsorption process of Cs⁺ on CuFC was best described by a pseudo-second order kinetic model, with a correlation coefficient (R ²) equal to 1.000, and the adsorption rate constant increased with increasing temperature. This result indicated that chemisorptions took place during the adsorption process. The adsorption equilibrium data fit well to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The mean adsorption energy (E) between 11 and 13 kJ/mol at different temperatures indicated that ion exchange was the main mechanism during the adsorption process. Thermodynamic parameters were also evaluated during the adsorption. The values of the standard Gibbs free energy change (ΔG ^o) and standard enthalpy change (ΔH ^o) suggested that the adsorption was a spontaneous and endothermic process. The distribution coefficient (K _d) was more than 2.94 × 10⁶ mL/g when the pH of solution was between 2.6 and 10.9, and the initial Cs⁺ concentration was 100 μg/L. The existence of K⁺ and Na⁺ did not affect the adsorption of Cs⁺ on CuFC when the concentration of K⁺ and Na⁺ in the solution was below 20 and 1,000 mg/L, respectively.     

Synthesis and characterization of ionic liquids: viologen bis{tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate} salts

Several viologen bis{tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate} salts were prepared by metathesis reaction of the corresponding viologen dibromides (diiodide) with sodium bis{tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate} salt in a polar organic solvent. They were characterized for their physical and thermal properties by experimental techniques including variable temperature X‐ray diffraction. All exhibited low T _g and T _m, and their T _g/T _m (K) ratios were in the range 0.66–0.79. Several exhibited polymorphism and formed isotropic ionic melts at <150°C. They were soluble in many common organic solvents such as ethers, alcohols, acetonitrile and methylene chloride. They exhibited photoluminescence in both 1,2‐dimethoxyethane and methanol, as well as in the solid state. In the solid state, the emission spectra exhibited hypsochromic shift when compared with those in solutions of 1,2‐dimethoxyethane and methanol.     

Synthesis and smectogenic properties of novel phloroglucinol-based star-shaped liquid crystals containing three peripheral alkyloxylated Schiff base arms

A series of symmetrical trimeric liquid crystalline compounds of which the molecular structure with a central core of 1,3,5-benzene attached by three rod-like mesogenic Schiff base moieties via the propylene spacers and ether linkages has successfully been synthesised and characterised by infra red and nuclear magnetic resonance spectroscopic techniques. All the star-shaped compounds in this series exhibit predominantly SmC phase except the analogue possessing terminal C₈H₁₇ group. It is apparent that the members with even parity from C₁₀H₂₁ to C₁₆H₃₃ show enantiotropic SmC phase while the member with longest terminal chain of C₁₈H₃₇ is inclined to monotropic smectogen. The X-ray diffraction measurements reveal that the tilted smectic layer structures of the SmC phase are confirmed to have an obvious sharp peak at small angles of 2θ ～ 1.03°–1.48° with d-spacing values of 4.01–4.58 nm, which are corresponding to tilt angles of ～48° in the SmC phase.