Dewetting of polymeric films: unresolved issues.

Since the early seminal theoretical work by Brochard and coworkers, and experiments by Reiter over a decade ago, considerable progress has been made toward the development of a comprehensive picture of the "equilibrium" and dynamic behavior of unstable thin polymeric films. Generally, theoretical work has carefully guided the design of many experiments conducted in this field. Recent experimental findings, however, raise new questions that could probably not have been foreseen by theory and now need to be revisited. In this paper we highlight three problems in two general areas, (1) the use of the effective interfacial potential describing film substrate interactions and (2) the dynamics of dewetting and the associated connection to "slip" phenomena and fingering instabilities. We suggest that in addition to experiments, analytical theory and simulations will play a critical role toward elucidating the ultimate goal of a universal picture of "equilibrium" and dynamic behavior of instabilities in thin films.

Influence of surface ordering on the wetting of structured liquids.

The substrate is shown to induce substantial ordering in diblock copolymer thin films above the bulk order-disorder transition (ODT) where, thermodynamically, a phase mixed state is favored. Initially, uniform films reorganize to form a hierarchy of transient surface patterns and stable film thicknesses that depend on the initial film thickness and on the substrate. Self-consistent field calculations of the free energy of the system for different situations, depending on the relative tendency for the different block components to be attracted to the substrate and/or free surface, provide an explanation of the formation of the stable film thicknesses. A continuum picture proposed earlier by Brochard et al. provides an explanation of the wetting characteristics of this system. In some cases the ordering destabilizes the film so that dewetting occurs (wetting autophobicity), whereas in other cases the surface ordering results in a kinetic stabilization of a film that would otherwise dewet.

Use of recombinant pp38 antigen of Marek's disease virus to identify serotype 1-specific antibodies in chicken sera by western blotting.

A fowlpox recombinant expressing the pp38 antigen of Marek's disease virus has been constructed. Production of pp38 in chick embryo fibroblasts (CEF) infected at a m.o.i. of 1 pfu/cell occurred over a period of 5 days and reached a peak at 72 h after infection. The pp38 antigen could be released from infected cells by freezing and thawing. Western blot analysis showed that denatured pp38 antigen reacted with antisera from chickens inoculated with serotype 1 MDV but failed to react with antisera from chickens inoculated with MDV serotype 2 or HVT. The results suggest that MDV pp38 contains a serotype 1-specific epitope which becomes available upon denaturation of the antigen and that this could be exploited to identify MDV-specific antibodies in epidemiological studies. The relationship between pp38 and the related polypeptides pp24 and pp41 in MDV-infected cells was also examined. The results suggest that pp24 and pp38 are synthesised independently and that MDV coded proteins (probably a protein kinase) might be required to convert pp38 to pp41.

A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase gene of Newcastle disease virus (NDV) protects chickens against challenge by NDV.

The hemagglutinin-neuraminidase (HN) gene from the Beaudette C strain of Newcastle disease virus (NDV) has been expressed in a recombinant fowlpox virus vector. The HN gene, under the control of the vaccinia p7.5 promoter, was inserted into a nonessential gene in the terminal inverted repeats of fowlpox virus. Expression was demonstrated in tissue culture, a protein of the correct size for fully glycosylated HN protein being recognized by an HN-specific monoclonal antibody on Western blots. When the recombinant fowlpox virus was inoculated into chickens by intravenous or wing-web routes, antibody which recognizes HN from purified NDV virions was produced. Protective immunity to NDV was generated in the chickens; at the highest dose of vaccine 100% of the chickens tested were protected against challenge with a virulent strain of NDV.

A fowlpox virus vaccine vector with insertion sites in the terminal repeats: demonstration of its efficacy using the fusion gene of Newcastle disease virus.

In this paper we report the development and testing of a fowlpox virus vector system. Insertion sites in non-essential regions within the terminal inverted repeats of the virus have been characterised. Foreign genes inserted into these sites are shown to be present in two copies in the resultant recombinant virus. To test the potential use of this vector as a live vaccine the fusion gene of Newcastle disease virus (NDV) has been inserted into a vaccine strain of fowlpox virus, and inoculated into chickens. The experiments demonstrate the ability of the recombinant to protect chickens against challenge by a virulent strain of NDV and to elicit the formation of anti-fusion protein antibody.

Insertion of the fusion gene from Newcastle disease virus into a non-essential region in the terminal repeats of fowlpox virus and demonstration of protective immunity induced by the recombinant.

In this paper we report on the identification of non-essential genes in the terminal repeats of the avipox-virus fowlpox virus and the use of these as insertion sites in a vector system. Foreign genes inserted into these sites are shown to be present in two copies in the resultant recombinant virus. To test the potential use of this vector as a live vaccine the fusion gene of Newcastle disease virus has been inserted into a vaccine strain of fowlpox virus and inoculated into chickens. The experiments demonstrate the ability of the recombinant to protect chickens against challenge by a virulent strain of Newcastle disease virus and to elicit the formation of an anti-fusion protein antibody.

Completion of the sequence of the genome of the coronavirus avian infectious bronchitis virus.

The nucleotide sequence determination of the genome of the Beaudette strain of the coronavirus avian infectious bronchitis virus (IBV) has been completed. The complete sequence has been obtained from 17 overlapping cDNA clones, the 5'-most of which contains the leader sequence (as determined by direct sequencing of the genome) and the 3'-most of which contains the poly(A) tail. Approximately 8 kilobases at the 3' end of this sequence have already been published. These contain the sequences of mRNAs A to E within which are the genes for the spike, the membrane and the nucleocapsid polypeptides: the main structural components of the virion. The remainder of the sequence, equivalent to the 'unique' region of mRNA F, is some 20 kilobases in length and is thought to code for a polymerase or polymerases which are involved in the replication of the genome and the production of the subgenomic messenger RNAs. This sequence contains two large open reading frames, potentially coding for polypeptides of molecular weights 441,000 and 300,000. Unlike other large open reading frames in the virus, the 300,000 open reading frame appears to have no subgenomic RNA associated with it which would allow it to be at the 5' end of an mRNA species. Because of this, and because of the characteristics of the sequence in the region immediately upstream of its start codon, other mechanisms of translation, such as ribosome slippage, must be postulated.