Approaches to the synthesis of 3-fluoroshikimic acids

Exploitation of the dual dehydrating and fluorodeoxygenating properties of the dialkylaminosulfurtrifluorides has allowed access to the C3-fluorinated analogues of (−)-shikimic acid.     

A measurement of the charge asymmetry in the decay η → π+π−γ

An experiment has been performed at the Rutherford Laboratory to look for a possible asymmetry in the decay η → π⁺π^?γ. The asymmetry for 34 680 eta decay is measured to be 0.012 ± 0.006, which is consistent with no C-violation in this decay mode.     

Non-convex dissipation potentials in multiscale non-equilibrium thermodynamics

Reformulating constitutive relation in terms of gradient dynamics (being derivative of a dissipation potential) brings additional information on stability, metastability and instability of the dynamics with respect to perturbations of the constitutive relation, called CR-stability. CR-instability is connected to the loss of convexity of the dissipation potential, which makes the Legendre-conjugate dissipation potential multivalued and causes dissipative phase transitions that are not induced by non-convexity of free energy, but by non-convexity of the dissipation potential. CR-stability of the constitutive relation with respect to perturbations is then manifested by constructing evolution equations for the perturbations in a thermodynamically sound way (CR-extension). As a result, interesting experimental observations of behavior of complex fluids under shear flow and supercritical boiling curve can be explained.     

In search of the ‘impenetrable’ volume of a molecule in a noncovalent complex

ABSTRACT

We propose to characterise the “impenetrable” volumes of molecules A and B in a complex A---B by finding that contour of its electronic density that separates the molecular surfaces of A and B but leaves them almost touching. The volume of the complex within that contour is always less than within the 0.001 au contour. The percent difference measures the interpenetration of the two molecules at equilibrium, and is found to directly correlate with the binding energy of the complex. We interpret the volume of each molecule that is enclosed by the almost-touching contour as that molecule's impenetrable volume relative to its particular partner. The percents by which the molecules' relative impenetrable volumes differ from their 0.001 au volumes in the free states also correlate with the strengths of the interactions. This allows the “absolute” impenetrable volume of any molecule to be estimated as ～25% of its 0.001 au volume in the free state. However this absolute impenetrable volume is only approached by the molecule in a relatively strong interaction.     

THE ACTION SPECTRUM OF AN IN VITRO DNA PHOTOREACTIVATION SYSTEM

Abstract— The wavelength-dependence of in vitro photoreactivation of transforming DNA by yeast extract has been determined. There is an intensity-dependent lag at the beginning of the biological reaction. There is a similar lag in the splitting of thymine dimers by the yeast extract in the light, a process known to account for most or all of the increase in transforming activity of photoreactivated DNA. The most efficient wavelengths for photoreactivation are around 3550 and 3850 Å. Although the action spectrum is not very similar to flavin absorption, riboflavin at very low concentration inhibits photoreactivation, as it also inhibits a number of flavoenzymes, suggesting that the photoreactivating enzyme might be a flavoprotein.     

Oxidative detagging of fluorous organosilanes

We have validated a novel detagging strategy featuring the unmasking of a fluorous-tagged silane to a hydroxy moiety. The fluorous silylated bicyclononane, prepared from the titanium-mediated annulation of 1-acetylcyclohexene and a fluorous-tagged allylsilane, was successfully detagged under Fleming-type oxidation conditions. The stereochemistry of the resulting hydroxylated product indicates retention of configuration upon detagging in line with the non-fluorous variant of this transformation.     

Scientists' Perspective on Introducing Authentic Inquiry to High School Teachers During an Intensive Three-Week Summer Professional Development Experience

The Information Technology in Science (ITS) Center for Teaching and Learning was a National Science Foundation funded program to provide high-quality professional development for 7–12th grade science teachers. The subgroup on which this paper focuses was immersed in an innovative approach to understanding chemistry of the environment. The group was comprised of 10 high school science teachers representative of science classes taught at all grade levels (9–12th). A team of four university professors led the group. The professors developed inquiry modules and communicated some of the intricacies of their research for adaptation to the participants' classrooms. This paper communicates the successful implementation and lessons learned by scientists during the course of an inquiry-based curriculum during summer 2005. The process and pace at which the material was covered, qualitative information about the attitudes of the participants towards the curriculum, and implications for professional development from the point of view of the science team leaders will be discussed. Analysis of time spent with participants revealed the progression and type of activities chosen for the professional development experience were effective. Results from informal participant interviews revealed they were most comfortable in incorporating inquiry into their classrooms after having been immersed in it themselves.     

Structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17α-yl acetate,C24H32O4

The X-ray structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17-yl acetate is reported. The crystals are monoclinic, space groupP2₁,Z=4,a=28.955(7),b=6.597(2),c=11.064(3) Å,/gb=90.80(2) °. The two crystallographically independent molecules have very similar overall geometries. The A rings have intermediate sofa-half-chair conformations and are bent relative to the steroid skeleton. The conformation of the 17-progesterone side chain is stabilized by the 17-ester substituent; the C(16)-C(17)-C(20)-O(20) torsion angle is –19.4(6) and –20.6(7)°.