Pairwise balanced designs whose line sizes do not divide six

A proper PBD(L, v) is a pairwise balanced design (with λ = 1) on v points whose line sizes are less than v and do not divide six. The existence or nonexistence of a proper PBD(L, v) is determined for all v different from thirty.     

The optical activity of the H-stretching vibrational modes of calycanthine and IRCD determinations of absolute configuration

The infrared circular dichroism (IRCD) due to the H-stretching vibrational modes of calycanthine originates principally from chromophore-substituent coupling and not from the degenerate interchromophore coupling mechanism particular to dissymmetric dimers. The general non-degenerate mechanism provides a procedure for the determination of absolute configuration from the IRCD associated with a localised characteristic vibrational mode.     

Level crossing in forward scattering by laser-polarization spectroscopy

A two-beam polarization method for sensitive detection of level crossing signals in laser forward scattering is described. As a demonstration a Hanle effect experiment has been performed on the 4f⁶6s6p ⁷F₁ level of Sm.     

Optical activity in chiral olefins : UV and CD spectra of some triterpenoid hydrocarbons

The UV and CD spectra of several related mono unsaturated steroidal and triterpenoid hydrocarbons have been measured. The electronic assignments are discussed and it is found that the Scott-Wrixon Rules can be successful in correlating the sign of the circular dichroism with molecular structure.     

Quantification of composition and domain sizes of industrial poly(phthalamide)/poly(dimethylsiloxane) block copolymers using different 1H solid state NMR methods

We have applied several 1H solid state NMR techniques to obtain structural information on industrial silicone copolymers as thermoplastic elastomers that proved difficult to be analysed by conventional techniques. Static measurements were applied to achieve the separation between mobile and rigid parts. To get structural information fast magic angle spinning at 25 kHz in combination with a high field of 700 MHz was used. 1H spin diffusion was applied to determine the domain sizes of the micro phase-separated polymer components.     

On the impulsive motion of a flat plate with suction

Summary The impulsive motion of a flat plate through a viscous incompressible fluid with time-dependent suction applied normally at the plate is considered. An approximate solution is obtained which describes the motion of the fluid during the initial stage of the motion of the plate, and also one which describes the motion at later stages when the suction velocity is large. The particular case when the suction velocity depends linearly on the time is considered in detail.     

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