From an Isolable Acyclic Phosphinosilylene Adduct to Donor‐Stabilized SiE Compounds (E=O,S, Se)

Reaction of the arylchlorosilylene‐NHC adduct ArSi(NHC)Cl [Ar=2,6‐Trip₂C₆H₃; NHC=(MeC)₂(NMe)₂C:] 1 with one molar equiv of lithium diphenylphosphanide affords the first stable NHC‐stabilized acyclic phosphinosilylene adduct 2 (ArSi(NHC)PPh₂), which could be structurally characterized. Compound 2 , when reacted with one molar equiv selenium and sulfur, affords the silanechalcogenones 4 a and 4 b (ArSi(NHC)(?E)PPh₂, 4 a : E=Se, 4 b : E=S), respectively. Conversion of 2 with an excess of Se and S, through additional insertion of one chalcogen atom into the Si?P bond, leads to 3 a and 3 b (ArSi(NHC)(?E)‐E‐P(?E)Ph₂, 3 a : E=Se, 3 b : E=S), respectively. Additionally, the exposure of 2 to N₂O or CO₂ yielded the isolable NHC‐stabilized silanone 4 c , Ar(NHC)(Ph₂P)Si?O.     

Universal Deformation Formulas

We give a conceptual explanation of universal deformation formulas for unital associative algebras and prove some results on the structure of their moduli spaces. We then generalize universal deformation formulas to other types of algebras and their diagrams.     

Computerized MRS voxel registration and partial volume effects in single voxel H-MRS

Partial volume effects in proton magnetic resonance spectroscopy in the brain have been studied previously in terms of proper water concentration calculations, but there is a lack of disclosure in terms of voxel placement techniques that would affect the calculations. The purpose of this study is to facilitate a fully automated MRS voxel registration method which is time efficient, accurate, and can be extended to all imaging modalities. A total of thirteen healthy adults underwent single voxel 1H-MRS scans in 3.0 T MRI scanners. Transposition of a MRS voxel onto an anatomical scan is derived along with a full calculation of water concentration with a correction term to account for the partial volume effects. Five metabolites (tNAA, Glx, tCr, mI, and tCho) known to yield high reliability are studied. Pearson’s correlation analyses between tissue volume fractions and metabolite concentrations were statistically significant in parietal (tCr, Glx, and tNAA) lobe and occipital lobe (tNAA). MRS voxel overlaps quantified by dice metric over repeated visits yielded 60% ~ 70% and coefficients of variance in metabolites concentration were 4% ~ 10%. These findings reiterate an importance of considering the partial volume effects when tissue water is used as an internal concentration reference so as to avoid misinterpreting a morphometric difference as a metabolic difference.     

Polymeric ruthenium bipyridine complexes: New potential materials for polymer solar cells

Methyl methacrylate‐containing bipyridine monomers were synthesized with a hydoxy‐functionalized bipyridine. The 4′‐methyl group of the 2,2′‐bipyridine was used to introduce hydoxy‐functionalized alkyl spacers of two different lengths. Two, different synthetic routes were applied for the preparation of the hydoxy‐functionalized bipyridine via a bromo‐(C₇ spacer) or a silylated‐(C₃ spacer) intermediate. A copolymer of poly(methyl methacrylate) with bipyridine units in the side chains was prepared by free‐radical copolymerization and characterized with ¹H NMR, ultraviolet–visible, and IR spectroscopy as well as gel permeation chromatography. The bipyridine units of the copolymer were reacted with ruthenium bipyridine precursors. The resulting graft copolymers displayed promising photophysical and electrochemical properties, opening interesting perspectives for applications in the field of solar‐cell devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 374–385, 2004     

Rheology/morphology interactions in polypropylene/polyamide-6 nanocomposites

Polypropylene/polyamide-6 (PP/PA-6) blends and their nanocomposites with unmodified and organically treated layered silicates (montmorillonite) were prepared in a melt compounding process to explore their mechanical performance. The rheology and morphology of these materials was studied. It could be shown that in all cases the inorganic filler enriched in the PA phase, resulting in a phase coarsening of the PP/PA nanocomposite as compared to the non-filled PP/PA blend. The mechanical properties of these nanoblends are consequently only slightly better than the pure polymers with respect to the modulus, while the impact level is below the pure polymers, reflecting the heterogeneity of the nanoblend.     

Interpretation of seasonal variation of metals and abiotic properties in a tropical lake using multivariate analysis and MINTEQA2 program.

The hydrological cycle of Lake Ipê and the principal parameters that could affect its abiotic parameters and its metal (Fe, Mn, and Cd) concentrations were investigated. A detailed study of seasonal variations using Principal Components Analysis (PCA) for the most relevant metals (Fe, Mn and Cd) was performed, assisted by the MINTEQA2 geochemical equilibrium program using 15 water abiotic parameters. The abiotic variables and metals in the lake were governed by the hydrological regimen of the Parana River and by the occurrence of occasional flood pulses and rainfall. The occurrence of cadmium is a concern; its presence could be due to industrial or agricultural activities or even to a natural geochemical process.     

New flavan and unusual chalcone glycosides from Drypetes parvifolia

Two new compounds 7-hydroxy-5-O-（β-D-glucopyranoside） flavan （1） and （Z）-4＇,6＇-dihydroxy-2＇-O-（β-D-glucopyranoside） chalcone （2）, along with eight known compounds, were isolated from the stem bark of Drypetes parvifolia （Euphorbiaceae）. Their structures were established on the basis of spectroscopic analysis and chemical evidence.     

Phase Transition of a Dicyanamide with Rutile‐like Structure: Syntheses and Crystal Structures of α‐ and β‐Cd[N(CN)2]2

Cadmium dicyanamide Cd[N(CN)₂]₂ was synthesized through aqueous ion exchange at room temperature. A reversible phase transition was detected by in situ X‐ray powder diffractometry above 55 °C. The crystal structures of both phases were determined by X‐ray powder diffraction (β‐Cd[N(CN)₂]₂: T = 22 °C, a = 621.60(3), b = 748.76(4), c = 770.21(5) pm, β = 91.784(3)°, P2₁/n (no. 14), Z = 2, wR_p = 0.063, R_p = 0.050, R_F = 0.059; α‐Cd[N(CN)₂]₂: T = 150 °C, a = 624.62(5), b = 752.92(6), c = 768.30(7) pm, Pnnm (no. 58), Z = 2, wR_p = 0.083, R_p = 0.064, R_F = 0.087). Both polymorphs consist of Cd²⁺ and bent planar [N(CN)₂]^— ions. α‐Cd[N(CN)₂]₂ crystallizes analogously to rutile and is isotypic with M^II[N(CN)₂]₂(M = Mg, Cr, Mn, Co, Ni, Cu). The monoclinic low‐temperature polymorph β‐Cd[N(CN)₂]₂ is closely related to that of the orthorhombic high‐temperature polymorph α‐Cd[N(CN)₂]₂ by a translationengleiche transition of index 2.     

Kakao

Analytical and Bioanalytical Chemistry -     

High Temporal Resolution Monitoring of Fermentations Using an On‐Line Amperometric Flow‐Through Microdetector

An on‐line microdetector containing amperometric biosensors was used for high temporal resolution (t_90%≈120 s) monitoring of glucose and ethanol concentrations during small scale fermentations. The ability of the microdetector to report on the effect of different experimental conditions was tested in fermentation processes carried out at 30 and at 37 °C. An increased ethanol production rate accompanied by an increased glucose consumption rate in the fermentation carried out at 37 °C was promptly revealed. Therefore, the microdetector proved to be an especially useful tool to monitor fermentations where the investigated processes are too fast to be followed by classical analytical approaches.