An antimicrobial sesterterpene from a Palauan sponge

An unidentified sponge from Palau contained the antimicrobial sesterpene $\text{1}$ that was identified by interpretation of spectral data and conversion into a degradation product of illimaquinone.     

Duct effects on the heave stability of plenum air cushions

Linear heave stability boundaries for a fun-duct-plenum air cushion suspension system are presented. These were obtained by using a quasi-static pressure-flow relationship for the fan, a finite element discretization for one dimensional unsteady duct flow, and a lumped capacitance model for the plenum. They indicate that even relatively short ducts can have a major effect at practical flow rates on the stability of cushion systems typically used for amphibious and overland operations. Some results obtained from a non-linear analysis, in which the method of characteristics was used for the duct flow, suggest that the linear approach should be adequate for practical stability calculations. Comparisons with lumped parameter models indicate that here the duct effect is associated primarily with the inertance of the air in the duct. It is also shown that for some operating conditions the duct-plenum system behaves as an Helmholtz resonator. Good agreement is obtained with an earlier transmission line analysis based on the wave equation.     

Measurement of high momentum transfer π−p → π0n at 5.9 GeV/c

The differential cross section for π^?p → π⁰n has been measured in the t range 1.8 ? |t| ? 8.2 (GeV/c)² by a counter-spark chamber experiment detecting the neutron and both π⁰ decay photons. A broad minimum was found, centered at |t| = 5.2 (GeV/c)².     

Spin polarization for electrons tunneling from MnxSb1−x

The spin polarization of electrons tunneling from Mn_xSb_1?x was measured over the full Mn concentration range 0 ? x ? 1. The polarization is positive and qualitatively similar to the magnetization per Mn atom of bulk material; for MnSb (x = 0.5) it is + 25%.