Palmadorin chemodiversity from the Antarctic nudibranch Austrodoris kerguelenensis and inhibition of Jak2/STAT5-dependent HEL leukemia cells

Detailed investigation of the Antarctic nudibranch Austrodoris kerguelenensis has resulted in the isolation of a diverse suite of new diterpenoid glyceride esters (1–16) related to the palmadorins (17–19), including one (palmadorin L (9)) that is the first halogenated diterpene from this well-studied nudibranch. Previous collections of A. kerguelenensis from McMurdo Sound, the Weddell Sea and the Western Antarctic Peninsula have afforded related diterpene glycerides, a natural product class implicated as a chemical defense in nudibranchs. In this paper we describe the isolation, structure elucidation, and stereochemical analysis of sixteen new palmadorins using a combination of one- and two-dimensional NMR techniques. Palmadorin A (17), B (18), D (1), M (10), N (11), and O (12) inhibit human erythroleukemia (HEL) cells with low micromolar IC₅₀'s, and palmadorin M inhibits Jak2, STAT5, and Erk1/2 activation in HEL cells and causes apoptosis, at 5 μM.     

Dynamical control: comparison of map and continuous-flow approaches

Continuous and pulsed forms of control of a multistable system are compared directly, both theoretically and numerically, taking as an example the switching of a periodically driven class-B laser between its stable and unstable pulsing regimes. It is shown that continuous control is the more energy efficient. This result is illuminated by making use of the close correspondence that exists between the problems of energy-optimal control and the stability of a steady state.     

Rogue waves in superfluid helium

Rogue waves have been observed in superfluid helium. The experimental system consists of high intensity second sound (temperature-entropy) waves within a resonant cavity. Under steady state conditions, with a constant oscillatory driving force at the resonant frequency, the waves are turbulent and there are fluxes of energy towards both high and low frequencies. Rogue waves appear under the nonequilibrium conditions that prevail shortly after the drive has been switched on, prior to establishment of the steady state. The experiment is described briefly, relevant results are presented and discussed theoretically in terms of nonlinear wave interactions, and possible connections to rogue waves on the ocean are considered.     

Quasi-monochromatic noise in bistable systems: The nature of large occasional fluctuations

Il Nuovo Cimento D - The response of an overdamped system to quasi-monochromatic (high-frequency narrow band) noise (QMN) has been investigated by means of analogue electronic experiments....