Fluorous linker facilitated synthesis of teichoic acid fragments

The use of perfluorooctylpropylsulfonylethanol as a new phosphate protecting group and fluorous linker is evaluated in the stepwise solution phase synthesis of a number of biologically relevant (carbohydrate substituted) glycerol teichoic acid fragments. Teichoic acid fragments, up to the dodecamer level, were assembled by means of phosphoramidite chemistry, using a relatively small excess of the building blocks and a repetitive efficient purification procedure of the protected intermediates by fluorous solid phase extraction (F-SPE).     

Experimental investigation of the nonequilibrium velocity distribution function in a heat conducting gas

Preliminary measurements of the nonequilibrium velocity distribution function in a heat conducting gas have been carried out using a Doppler broadened absorption line. The experimental technique, which uses the coincidence of a Stark tunable line of NH₂D and the CO₂ P(20) laser frequency, is described. For molecular velocities that are not too high, the results are in good agreement with the Chapman-Enskog solution of the Boltzmann equation.     

A comparison of data on the viscomagnetic effect, flow birefringence and depolarized Rayleigh line broadening

A comparison of data on the viscomagnetic effect, flow birefringence and depolarized Rayleigh line broadening for various gases of linear molecules at temperatures between 90 and 293 K is carried out. From the combined results information is obtained on the scalar structure of the non-equilibrium angular momentum polarization produced in viscous flow.     

Kinetic theory of field effects in nonuniform molecular gases

Effects of magnetic and electric fields on transport phenomena in dilute polyatomic gases are reviewed within the framework of first order Enskog theory. The established technique of approximate operator inversion is used to give first order approximations of the transport coefficients. Instead of the customary expansion of polarization into orthogonal polynomials a more general treatment is chosen here so as to accomodate recent experimental observations. The polarizations produced by macroscopic fluxes are assumed to be eigenfunctions of the collision operator within the subspace of functions anisotropic in angular momentum. The formalism is extended to mixtures in a way to let the final expressions assume the same form as for pure gases. The obtained transport coefficients obey several symmetry relations and inequalities. Additional inequalities are now also derived for the matrix describing the saturated field effects.     

Flow birefringence in gases: The temperature dependence

A method is described for measurements of the temperature dependence of flow birefringence in gases between 90 and 293 K. Results are presented for CO, N₂, HD and oD₂.     

The Senftleben-Beenakker effect in ammonia and its mixtures with noble gases

Experimental results are presented for the influence of a magnetic field on the viscosity of NH₃-He and NH₃-Ar and on the thermal conductivity of NH₃-Ar gas mixtures. Data are reported for various mixture compositions at room temperature. The data are analyzed in detail in an attempt to clarify the unique behavior of ammonia.     

Emission of polarization-entangled microwave photons from a pair of quantum dots

We describe a mechanism for the production of polarization-entangled microwaves using intraband transitions in a pair of quantum dots. This proposal relies neither on spin-orbit coupling nor on control over electron-electron interactions. The quantum correlation of microwave polarizations is obtained from orbital degrees of freedom in an external magnetic field. We calculate the concurrence of emitted microwave photon pairs and show that a maximally entangled Bell pair is obtained in the limit of weak interdot coupling.     

Manipulation of photon statistics of highly degenerate incoherent radiation

Highly degenerate incoherent radiation has a Gaussian density matrix and a large occupation number of modes f. If it is passed through a weakly transmitting barrier, its counting statistics is close to Poissonian. We show that a second identical barrier, in series with the first, drastically modifies the statistics. The variance of the photocount is increased above the mean by a factor f times a numerical coefficient. The photocount distribution reaches a limiting form with a Gaussian body and highly asymmetric tails. These are general consequences of the combination of weak transmission and multiple scattering.