J. van der Veen

Dependence of the clearing temperature on alkyl chain length in nematic homologous series

Abstract In homologous series of nematic compounds with relatively high clearing temperatures, these temperatures are known to decrease with increasing chain length. Recently, however, series with relatively low clearing temperatures have been synthetized in which these temperatures increase with increasing chain length. In both cases the clearing temperatures alternate within a series. A qualitative explanation is given for these facts. The discussion is based on an expression for the free energy in which both the attractive dispersion forces and the excluded volume affects are taken into account.

Vanadyl phthalocyanine: An organic material for optical data recording

Vanadyl Phthalocyanine (VOPc) is a stable organic dye which absorbs in the spectral range of currently available injection lasers. The applicability for high density optical storage of single, double and triple layer structures containing a thin film of this dye, is investigated. It is concluded that if VOPc is used in combination with a tellurium film, some power reduction relative to single Te films can be achieved.

Molecular Structure and Nematic Liquid Crystalline Behaviour

Abstract In this review some experimental results on the variation of the nematic-isotropic transition temperature TN1 with molecular structure will be evaluated with the aid of expressions for TN1 from molecular-statistical theories. The effect of terminal substituents on TN1 and some typical trends in the values of TN1 for the members of homologous series can be understood from changes in the anisotropic dispersion forces as discussed in Maier and Saupes theory. The effects of some other structural changes in the molecules on TN1, as for example the variation of central groups, cannot be explained on this basis. Probably it is necessary to take into account as well the molecular repulsions due to the excluded volume.

Experimental infection with mouse adenovirus in adult mice

Intraperitoneal inoculation of adult mice with mouse adenovirus caused a generalized infection with occasional deaths. Virus was found widely distributed in several tissues as well as in white blood cells from the third day after inoculation. L cells were used for viral recovery and assay. The highest viral titers were reached in the spleen. No virus was detected in tissues and white blood cells after 2 weeks. In contrast, virus was demonstrated in the urine by the 14th day and viruria persisted for as long as 2 years. A similar picture was found after intranasal inoculation. The failure to demonstrate virus in tissues after the early weeks of infection was probably due to the production of high levels of antibody for up to 2 years.

Single Wavelength Optical Recording In Pure, Solvent Coated Infrared Dye Layers

Results are presented of substrate incident optical recording experiments at A1GaAs laser wavelengths on pure, amorphous, solvent coated, dye layers. Upon laser irradiation pits with a rim are formed, which increase in width and depth with increasing pulse energy. The information is read out at the recording wavelength as reflection changes relative to the dye layer reflection.

Instabilities in electric fields of a nematic liquid crystal with large negative dielectric anisotropy

Abstract A new nematic α-cyanostilbene with a dielectric of about − 5 is invesitigated in AC fields. On increasing the voltage in the conduction regime the instabilities disappear at a field threshold. In addition, chevrons can be observed over the whole frequency range.

Surface band structure of MBE-grown GaAs(001)-2 × 4

Angle-resolved photoemission measurements using synchrotron radiation have been performed for the As-stable GaAs(001)-2 × 4 reconstruction, which was grown in situ by molecular beam epitaxy. Measurements made at high symmetry points and along symmetry lines of the surface Brillouin zones show weakly dispersing dangling bond-like surface states in the energy range between -1.6 eV and the top of the valence band and a nearly dispersionless state near -3 eV.

Liquid Crystalline Bridge Substituted Schiff Bases

Abstract The preparation and mesomorphic behaviour of some imidoyl cyanides is reported. Their general formula is: They are yellow stable compounds. Due to the strongly nonplanar conformation they show lower clearing temperatures than the analogous Schiff bases. However their melting points are in general higher. Consequently only monotropic nematic behaviour is observed. The dielectric anisotropy is small positive.

Homotypic and heterotypic antibody response in infants to adenovirus vaccine

Two or three doses of inactivated monkey kidney tissue culture propagated adenovirus vaccine containing types 3, 4 and 7, or three doses of placebo fluid were administered to 271 infants 3 to 12 months of age. Vaccination was not associated with any clinical reactions. The first dose of vaccine produced a poor response, whereas the second and third doses stimulated high levels of neutralizing antibody to types 3, 4 and 7. The response in infants without pre-existing antibody did not deviate significantly from that in initially antibody-positive infants. Three doses of vaccine were found to produce neutralizing antibody in 97—100% of the infants. Antibody persisted for at least one year in 70—100% of 35 infants studied, although the titers decreased substantially. Low levels of heterotypic antibody to types 14 and 21 developed in, respectively, 76% and 18% of initially antibody-negative infants after two or three doses of vaccine. The neutralizing antibody response observed 6 months after administration of one dose of vaccine was substantially higher than that found one month after the first injection.

Antibody response against strains of influenza-A virus in ferrets with basic immunity

SummaryIn Holland ferrets are offered for sale with basic antibodies against one or more sub-groups of strains of influenza-A virus. With the haemagglutination inhibition test low basic antibody titers can only be detected by neutralising the non-specific inhibitor in the ferret sera. When such a ferret is infected with a strain of a heterologous sub-group, a considerable rise in antibodies is obtained against the homologous and heterologous sub-groups. It is very probable that the same holds for human beings. Some examples are given of haemagglutination-inhibition tests with serum pairs from adults who suffered from influenza in the epidemic of the winter of 1949 in Holland from which the non-specific inhibitor had been eliminated.