Ice structuring proteins - a new name for antifreeze proteins

Antifreeze proteins (AFPs) have been reported in the academic literature for many years, and are increasingly arousing interest in the technical and popular media, particularly because of their potential applications. However, the term "antifreeze" does not always accurately describe their natural function, or their application in frozen systems, where they do not prevent freezing, but control the size, shape and aggregation of ice crystals. We survey the properties and applications of AFPs and propose a more generally applicable name based on the fact that all AFPs bind to ice and consequently influence crystal growth and interactions: "Ice Structuring Proteins".     

Amidrazones V. thermolysis of N1-benzyl-substituted amidrazone ylides

Thermolysis of 1,1-dimethyl-1-benzyl-2-(iminophenylmethyl)hydrazinium hydroxide inner salt gave dimethylamine, 2,4,6-triphenyl-s-triazine and 2,4,6-triphenyl-1,2-dihydro-s-triazine.     

Chain dimensions in plastically deformed semicrystalline polymers

The effect of plastic deformation on the chain dimensions of polymers in the semicrystalline state was investigated using linear hydrogenated polybutadiene (HPB), a model ethylene/butene-1 copolymer having about 40% crystallinity at room temperature. Dilute blends of deuterium-labeled chains with various molecular weights (20,000 ≤ M ≤ 214,000) in the same unlabeled matrix (M = 95,000) were uniaxially stretched at 25°C to extension ratios of α = 2.4 and 4.4. Radius of gyration normal to the stretch direction R_⊥ was measured for the labeled chains by small-angle neutron scattering. The molecular extension ratio inferred from these data α_m = R/R was significantly smaller than α for short chains (M < 50,000) but increased to the affine range α_m = α for M > 100,000. This variation in α_m/α closely parallels the molecular weight dependence of mechanical strength and ductility in HPB over the same range.     

The electrical and optical properties of amorphous germanium-gallium alloys

The paper extends an earlier study of the far infrared properties of a series of evaporated amorphous GeGa alloys. The results of temperature dependent dc resistivity and near infrared and visible optical experiments are presented. Since the properties of amorphous films are dependent on the preparation conditions, a technique has been developed in which four samples of varying composition are prepared in the same evaporation. The far infrared data indicate that a significant fraction of Ga atoms dissolve in a-Ge with four-fold coordination. However, there is also indirect evidence of mixed valence.     

Asymmetric epoxidation of cis-alkenes mediated by iminium salts: highly enantioselective synthesis of levcromakalim

[reaction: see text] A range of cis-substituted olefins has been epoxidized with a new dihydroisoquinolinium salt catalyst, using tetraphenylphosphonium monoperoxysulfate as the stoichiometric oxidant, giving ee's of up to 97%. The reaction has been used as the key step in an enantioselective synthesis of the antihypertensive agent levcromakalim.     

Electrosynthesis of cyclic carbonates from epoxides and atmospheric pressure carbon dioxide

The use of CO(2) for the preparation of value-added compounds has dramatically increased due to increased global warming concerns. We herein report an electrochemical cell containing a copper cathode and a magnesium anode that effectively converts epoxides and carbon dioxide to cyclic carbonates under mild electrochemical conditions at atmospheric pressure.     

Determining spin through quantum azimuthal-angle correlations

Determining the spin of new particles is critical in identifying the true theory among various extensions of the Standard Model at the next generation of colliders. Quantum interference between different helicity amplitudes was shown to be effective when the final state is fully reconstructible. However, many interesting new physics processes allow only for partial reconstruction. In this Letter, we show how the interference effect can be unambiguously extracted even in processes that have two-fold ambiguity, by considering the correlation between two decay planes in e⁺e⁻$e^{+}{e}^{-}$ collisions.     

Ferrocene and Porphyrin Monolayers on Si(100) Surfaces: Preparation and Effect of Linker Length on Electron Transfer

The missing link : Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.

     

The photodegradation of cadmium yellow paints in Henri Matisse’s Le Bonheur de vivre (1905–1906)

Evidence for the alteration of the yellow paints in Henri Matisse’s Le Bonheur de vivre (1905–1906, The Barnes Foundation) has been observed since the 1990s. The changes in this iconic work of Matisse’s Fauvist period include lightening, darkening, and flaking of the yellow paints. Handheld X-ray fluorescence (XRF) and multispectral imaging surveys reveal that the degradation is confined to cadmium yellow (CdS) paints. The discoloration of cadmium yellow paints in Impressionist, Post-Impressionist and early modernist work from the 1880s through the 1920s has been ascribed to the photo-oxidative degradation of CdS. Preliminary investigations of the degraded yellow paints in this work involved Cd L_III-edge X-ray Absorption Near Edge Spectroscopy (XANES) at the Stanford Synchrotron Radiation Light Source (SSRL Menlo Park, California) and Scanning Electron Microscopy-energy dispersive X-ray analysis (SEM-EDS) at the Winterthur Museum Scientific Research and Analysis Laboratory. To determine if the visual changes in the paints did in fact indicate photo-oxidative degradation and if different chemistries could be observed for the lightened versus darkened regions, synchrotron radiation-micro Fourier Transform InfraRed (SR-μFTIR) spectroscopy, X-ray Fluorescence (SR-μXRF) mapping and micro X-ray Absorption Near Edge Spectroscopy (μXANES) mapping at the Cd L_III-edge of the altered paint cross-sections were carried out at the European synchrotron radiation facility (ESRF, Grenoble, France) beamline ID-21. The goal is to elucidate the discoloration mechanisms observed in the paint using elemental and speciation mapping. The μXANES mapping and SR-FTIR imaging showed a substantial enrichment of CdCO₃ in the off-white surface crust of the faded/discolored CdS paint. This suggests that the CdCO₃ is present as an insoluble photodegradation product rather than solely a paint filler or starting reagent. Additionally, oxalates and sulfates were found to be concentrated at the alteration surface.