Polarization dependence of vibrational coupling signals in femtosecond stimulated Raman spectroscopy

The polarization dependence of vibrational coupling signals seen in femtosecond stimulated Raman spectroscopy (FSRS) is investigated. Changing the polarization of a pulse used to impulsively excite coherent low frequency chlorine bending motion in CDCl(3) has a dramatic effect on the line shape of vibrational sidebands which arise from the anharmonic coupling of the pumped modes at 262 and 365 cm(-1) with the higher frequency symmetric stretching mode at 652 cm(-1). The asymmetric bend sideband (652+262 cm(-1)) changes sign and magnitude as the impulsive pulse polarization is rotated relative to the Raman pulses, while the symmetric bend sideband (652+365 cm(-1)) is relatively polarization independent. These experiments demonstrate the ability of FSRS to obtain time-resolved information on not only the vibrational coupling strength but also the symmetry of anharmonically coupled modes.     

Redox Non‐Innocent Behavior of a Terminal Iridium Hydrazido(2−) Triple Bond

The synthesis of the first terminal Group 9 hydrazido(2‐) complex, Cp*IrN(TMP) ( 6 ) (TMP=2,2,6,6‐tetramethylpiperidine) is reported. Electronic structure and X‐ray diffraction analysis indicate that this complex contains an Ir?N triple bond, similar to Bergman's seminal Cp*Ir(N^tBu) imido complex. However, in sharp contrast to Bergman's imido, 6 displays remarkable redox non‐innocent reactivity owing to the presence of the N_β lone pair. Treatment of 6 with MeI results in electron transfer from N_β to Ir prior to oxidative addition of MeI to the iridium center. This behavior opens the possibility of carrying out facile oxidative reactions at a formally Ir^III metal center through a hydrazido(2?)/isodiazene valence tautomerization.     

A Comment on the Outgoing Radiation Condition for the Gravitational Field and the Peeling Theorem

The connection between the Bondi-Sachs (BS) andthe Newman-Penrose (NP) framework for the study of theasymptotics of the gravitational field is done. Inparticular the coordinate transformation relating the BS luminosity parameter and the NP affineparameter is obtained. Using this coordinatetransformation it is possible to express BS quantitiesin terms of NP quantities, and to show that if theOutgoing Radiation Condition is not satisfied then thespacetime will not decay in the way prescribed by thePeeling theorem.     

A “Coprolitic Vision” for Earth Science Education

William Buckland (1784–1846) first identified and scientifically studied coprolites in the early 1820s. Although some of his contemporaries did not look favorably upon him or his research, Buckland's early experiments advanced paleoecology and taphonomy. Because our informal presentations with coprolites resulted in students' spirited reactions, we investigated whether coprolite introduction, accompanied with its history of science, had potential for meaningful learning in K‐12 Earth Science classrooms. Practicing Earth Science teachers (N = 28) enrolled in an online paleontology course researched coprolites, identified potential student interest, and designed coprolite activities for their individual classrooms. Resulting projects were diverse and creative, and incorporated investigations into fossilization processes, paleoenvironments, food chains, and geologic time. In anonymous surveys, teachers indicated that their students' interest in coprolites is high. We propose inclusion of coprolites and their history in Earth Science classrooms as a portal to hook students' interest and as springboard to additional scientific topics.     

Vibrational dephasing in highly compressed liquid nitrogen studied with time-resolved stimulated raman gain spectroscopy

Abstract

In liquid nitrogen at 295 K we observe for the first time the minimum in the variation of the vibrational dephasing rate T^?1 ₂ with density at ρ = 2.15 × 10²². cm^?3. At higher densities the dephasing rate shows a steep rise with density. The observed behaviour shows good agreement with results of previously published molecular dynamics simulations.     

Discovery of a Potent Allosteric Kinase Modulator by Combining Computational and Synthetic Methods

The rational design of allosteric kinase modulators is challenging but rewarding. The protein kinase PDK1, which lies at the center of the growth‐factor signaling pathway, possesses an allosteric regulatory site previously validated both in vitro and in cells. ANCHOR.QUERY software was used to discover a potent allosteric PDK1 kinase modulator. Using a recently published PDK1 compound as a template, several new scaffolds that bind to the allosteric target site were generated and one example was validated. The inhibitor can be synthesized in one step by multicomponent reaction (MCR) chemistry when using the ANCHOR.QUERY approach. Our results are significant because the outlined approach allows rapid and efficient scaffold hopping from known molecules into new easily accessible and biologically active ones. Based on increasing interest in allosteric‐site drug discovery, we foresee many potential applications for this approach.