The Methanol-Trimethoxyborane Azeotrope as a Solvent

The methanol-trimethoxyborane azeotrope is an ea.sily prepa. red solvent of strong H-bond donor and weak H-bond acceptor properties. It has a low viscosity and low boiling point, and is completely transparent in the visible and uv at wave lengths above 220 nm. It has a dieLectric constant of 9 and ion pair formation constants between 103 and 104 for simple electrolytes. The glass electrode pH-meter can be used in this solvent, with the ordinary calomel reference electrode. Indicator acidity measurements are somewhat complicated by the forma•tion of H-bonded ion pairs. The solvent is useful for measuning the relative acidity of strong acids; CH3S020H and CF3S020H are readily differentiated. It should be useful for other physico-chemical measurements and also in preparative chemistry

The Methanol-Trimethoxyborane Azeotrope as a Solvent for Acid-Catalyzed Reactions. Methyl Esterification

Carboxylic acids UIIldergo a rapid and complete acid-catalyzed methyl esterification in the methanol-trimethoxyborane azeotrope. The reaction is first order in cariboxylic acid and first order in strong acid catalyst. Rate constants are very similar to those in methanol alone. These observations suggest that the mechanism is the same as that in solvent, methanol-AAc 2. The reaction can be made the basis of a convenient preparation of methyl esters. It has been used to prepare methyl benzoate, methyl lactate, and the methyl ester of phenylalanine. Acid-catalyzed acetal and ketal formation in the azeotrope is fast but incomplete. Methyl etherification of tertiary alcohols seems too limited, structurally, to be generally useful. No acid-catalyzed addition of methanol to acetonitrile or acrylonitrile could be observed

The Methanol-Trimethoxyborane Azeotrope as a Solvent

The methanol-trimethoxyborane azeotrope is an ea.sily prepa. red solvent of strong H-bond donor and weak H-bond acceptor properties. It has a low viscosity and low boiling point, and is completely transparent in the visible and uv at wave lengths above 220 nm. It has a dieLectric constant of 9 and ion pair formation constants between 103 and 104 for simple electrolytes. The glass electrode pH-meter can be used in this solvent, with the ordinary calomel reference electrode. Indicator acidity measurements are somewhat complicated by the forma•tion of H-bonded ion pairs. The solvent is useful for measuning the relative acidity of strong acids; CH3S020H and CF3S020H are readily differentiated. It should be useful for other physico-chemical measurements and also in preparative chemistry

Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3)

We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using the time-resolved magneto-optical Kerr effect. The FMR oscillations in the time-domain appear in response to a sudden, optically induced change in the direction of easy-axis anistropy. The high FMR frequency, 250 GHz, and large Gilbert damping parameter, alpha ~ 1, are consistent with strong spin-orbit coupling. We find that the parameters associated with the magnetization dynamics, including alpha, have a non-monotonic temperature dependence, suggestive of a link to the anomalous Hall effect.Comment: submitted to Phys. Rev. Let

Determination of the spin-flip time in ferromagnetic SrRuO3 from time-resolved Kerr measurements

We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO3. We observe that the demagnetization time slows substantially at temperatures within 15K of the Curie temperature, which is ~ 150K. We analyze the data with a phenomenological model that relates the demagnetization time to the spin flip time. In agreement with our observations the model yields a demagnetization time that is inversely proportional to T-Tc. We also make a direct comparison of the spin flip rate and the Gilbert damping coefficient showing that their ratio very close to kBTc, indicating a common origin for these phenomena

Interleukin-1 receptor-associated kinase-M suppresses systemic lupus erythematosus

Interleukin-1 receptor-associated kinase (IRAK)-M suppresses Toll-like receptor (TLR)-mediated activation of innate immunity during infection. A similar role was hypothesised for IRAK-M in autoimmunity

Cultural factors that affected the spatial and temporal epidemiology of kuru

Kuru is a prion disease which became epidemic among the Fore and surrounding linguistic groups in Papua New Guinea, peaking in the late 1950s. It was transmitted during the transumption (endocannibalism) of dead family members at mortuary feasts. In this study, we aimed to explain the historical spread and the changing epidemiological patterns of kuru by analysing factors that affected its transmission. We also examined what cultural group principally determined a family’s behaviour during mortuary rituals. Our investigations showed that differences in mortuary practices were responsible for the initial pattern of the spread of kuru and the ultimate shape of the epidemic, and for subsequent spatio-temporal differences in the epidemiology of kuru. Before transumption stopped altogether, the South Fore continued to eat the bodies of those who had died of kuru, whereas other linguistic groups, sooner or later, stopped doing so. The linguistic group was the primary cultural group that determined behaviour but at linguistic boundaries the neighbouring group’s cultural practices were often adopted. The epidemiological changes were not explained by genetic differences, but genetic studies led to an understanding of genetic susceptibility to kuru and the selection pressure imposed by kuru, and provided new insights into human history and evolution