Modeling the molecular weight distribution of block copolymer formation in a reversible addition-fragmentation chain transfer mediated living radical polymerization

Block copolymers have become an integral part of the preparation of complex architectures through self-assembly. The use of reversible addition-fragmentation chain transfer (RAFT) allows blocks ranging from functional to nonfunctional polymers to be made with predictable molecular weight distributions. This article models block formation by varying many of the kinetic parameters. The simulations provide insight into the overall polydispersities (PDIs) that will be obtained when the chain-transfer constants in the main equilibrium steps are varied from 100 to 0.5. When the first dormant block [polymer-S-C(Z)=S] has a PDI of 1 and the second propagating radical has a low reactivity to the RAFT moiety, the overall PDI will be greater than 1 and dependent on the weight fraction of each block. When the first block has a PDI of 2 and the second propagating radical has a low reactivity to the RAFT moiety, the PDI will decrease to around 1.5 because of random coupling of two broad distributions. It is also shown how we can in principle use only one RAFT agent to obtain block copolymers with any desired molecular weight distribution. We can accomplish this by maintaining the monomer concentration at a constant level in the reactor over the course of the reaction. (c) 2005 Wiley Periodicals, Inc.

Sequence and tissue distribution of chicken cellular nucleic acid binding protein cDNA

We sequenced cDNAs coding for chicken cellular nucleic acid binding protein (CNBP). Two slightly different variations of the open reading frame were found, each of which translates into a protein with seven zinc finger domains. The longest transcript contains an in-frame insert of 3 bp. The sequence conservation between chick CNBP cDNAs with human, rat and mouse CNBP cDNAs is extreme, especially in the coding region, where the deduced amino acid sequence identity with human, rat and mouse CNBP is 99%. CNBP-like transcripts were also found in various tissues from insect, shrimp, fish and lizard. Regions with remarkable nucleotide conservation were also found in the 3' untranslated region, indicating important functions for these regions. Quantitative reverse transcription polymerase chain reaction (RT-PCR) indicated that in the chick, CNBP is present in all tissues examined in approximately equal ratios to total RNA. RT-PCR of total RNA isolated from different phyla indicate CNBP-like proteins art widespread throughout the animal kingdom. The extraordinary level of conservation suggests an important physiological role for CNBP. (C) 1997 Elsevier Science Inc.

Distribution of interleukin-2,-4,-10, tumour necrosis factor-alpha and transforming growth factor-beta mRNAs in oral lichen planus

In the present study. MRNA for the cytokines interleukin-2 (IL-2), IL-4, IL-10 tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor beta-1 (TGF-beta-1) were investigated in oral lichen planus (OLP) lesions using in situ hybridization with S-35-labelled oligonucleotide probes on frozen tissue sections. In addition, the expression of interferon-gamma (IFN-gamma), IL-10 and IL-4 mRNAs was analysed in cultured lesional T lymphocytes from oral lichen planus by polymerase chain reaction. Cells expressing mRNA for IL-2, IL-4, IL-10, TNF-alpha and TGF-beta(1) were found in all the biopsies studied. Approximately 1-2% of the total number of infiltrating cells in the lesions were positive for each of the different cytokine mRNAs. Most biopsies contained basement membrane-oriented, mRNA-positive cells. In the cultured T-cell lines, message for IFN-gamma was detected in all the patients, IL-10 in all but one, and IL-4 in just one of the seven patients investigated. The results suggest that mRNA for both pro- and anti-inflammatory cytokines, i.e., mixed T-helper 1 (T(H)1) and T(H)2 cytokine profiles, are generated simultaneously by a limited number of cells in chronic lesions of OLP. (C) 1999 Elsevier Science Ltd. All rights reserved.

Heterogeneous distribution of isoactins in cultured vascular smooth muscle cells does not reflect segregation of contractile and cytoskeletal domains

We have previously demonstrated that or-smooth muscle (alpha -SM) actin is predominantly distributed in the central region and beta -non-muscle (beta -NM) actin in the periphery of cultured rabbit aortic smooth muscle cells (SMCs). To determine whether this reflects a special form of segregation of contractile and cytoskeletal components in SMCs, this study systematically investigated the distribution relationship of structural proteins using high-resolution confocal laser scanning fluorescent microscopy. Not only isoactins but also smooth muscle myosin heavy chain, alpha -actinin, vinculin, and vimentin were heterogeneously distributed in the cultured SMCs. The predominant distribution of beta -NM actin in the cell periphery was associated with densely distributed vinculin plaques and disrupted or striated myosin and ol-actinin aggregates, which may reflect a process of stress fiber assembly during cell spreading and focal adhesion formation. The high-level labeling of alpha -SM actin in the central portion of stress fibers was related to continuous myosin and punctate alpha -actinin distribution, which may represent the maturation of the fibrillar structures. The findings also suggest that the stress fibers, in which actin and myosin filaments organize into sar-comere-like units with alpha -actinin-rich dense bodies analogous to Z-lines, are the contractile vimentin structures of cultured SMCs that link to the network of vimentin-containing intermediate alpha -actinin filaments through the dense bodies and dense plaques.

Ecological distribution of mosquito larvae of the Anopheles punctulatus group on Niolam (Lihir) Island, Papua New Guinea

We surveyed the larval habitats of member,, of the Anopheles punctulatus group of mosquitoes on Niolam (Lihir) Island. Papua New Guinea. Identification of this group was undertaken by polymerase chain reaction-restriction fragment length polymorphism analysis of the amplified internal transcribed spacer unit 2 of rDNA. because morphologic separation of member species is unreliable. The most widespread malaria vector species and their most common larval habitats identified to aid source-reduction programs for malaria control. The most ubiquitous species was An. punctulatus, followed by An. farauti no. 2. then An. farauti s.s. Anopheles punctulatus has increased relative to An.farauti s.l. since the start of development projects on Lihir Island. The most common larval habitats were shallow temporary pools with clay substrate and with plants or floatage. These habitats. mostly encountered alongside poorly drained roads, may be increased by development projects.

Supply chain management as beyond operational efficiency

The orthodoxy of supply chain management (SCM) emphasises competitive advantage through increased operational efficiency and market responsiveness from production and distribution processes into the hands of consumers. It anticipates that future competition will be between chains rather than between firms. While well established in other industry sectors, the SCM concept is newly developed in the Australian agri-food sector. Critical review of the concept has identified key issues of power among channel members, processes of chain initiation and innovation, and the inability of SCM to offer a viable business strategy for some firms. Building on those insights, this paper examines the supply chain concept for horticulture. Horticultural products are characterised by perishability, heterogeneity and lags in production response to market signals. Producers’ profits are vulnerable to quantity, timing of supply and product specification. Many supply chains in smaller industries are loose, fragmented, interwoven, unstable and unique! Firms operating within these environments need an astute understanding of the chains, the hierarchy of channel members and their relative position. Effective business strategies – for individual firms and supply chains - need to be developed and redeveloped to accommodate the dynamic nature of horticulture. Two case studies are discussed as contributions to this early stage of the theoretical development of supply chain management. The SCM concept also has implications for horticultural researchers, involving a wider range of industry stakeholders, technical problems and research skills. As for business management, the usefulness of the concept will depend on its capacity to increase responsiveness to customers’ preferences and customer value.

Speciation and distribution of the members of the Anopheles punctulatus (Diptera : Culicidae) group in Papua New Guinea

Mosquito collections were made throughout the mainland of Papua New Guinea to identify the members of the Anopheles punctulatus group present and to determine their distribution. Identification was made using morphology, DNA hybridization, and polymerase chain reaction (PCR)-RFLP analysis. Nine members of the group were identified: An. farauti s.s. Laveran, An.farauti 2, An. koliensis Owen, and An. punctulatus Donitz, were common and widespread; An. farauti 4 was restricted to the north of the central ranges where it was common; An. farauti 6 was found only in the highlands above 1,000 m; and An. farauti 3, An. sp. near punctulatus and An. clowi Rozeboom & Knight were uncommon and had restricted distributions. Identification of An. koliensis and An. punctulatus using proboscis morphology was found to be unreliable wherever An. farauti 4 occurred. The distribution and dispersal of the members of the An. punctulatus group is discussed in regard to climate, larval habitats, distance from the coast, elevation, and proximity to human habitation.

Development and evaluation of a species diagnostic polymerase chain reaction-restriction fragment-length polymorphism procedure for cryptic members of the Culex sitiens (Diptera : Culicidae) subgroup in Australia and the southwest Pacific

Members of the Culex sitiens subgroup are important vectors of arboviruses, including Japanese encephalitis virus, Murray Valley encephalitis virus and Ross River virus. Of the eight described species, Cx. annulirostris Skuse, Cx. sitiens Wiedemann, and Cx. palpalis Taylor appear to be the most abundant and widespread throughout northern Australia and Papua New Guinea (PNG). Recent investigations using allozymes have shown this subgroup to contain cryptic species that possess overlapping adult morphology. We report the development of a polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) procedure that reliably separates these three species. This procedure utilizes the sequence variation in the ribosomal DNA ITS1 and demonstrates species-specific PCR-RFLP profiles from both colony and field collected material. Assessment of the consistency of this procedure was undertaken on mosquitoes sampled from a wide geographic area including Australia, PNG, and the Solomon Islands. Overlapping adult morphology was observed for Cx. annulirostris and Cx. palpalis in both northern Queensland and PNG and for all three species at one site in northwest Queensland.

Polymerase chain reaction tests for the identification of Ross River, Kunjin and Murray Valley encephalitis virus infections in horses

Objective To develop and validate specific, sensitive and rapid diagnostic tests using RT-PCR for the detection of Ross River virus (RRV), Kunjin virus (KV) and Murray Valley encephalitis virus (MVEV) infections in horses. Methods Primer sets based on nucleotide sequence encoding the envelope glycoprotein E2 of RRV and on the nonstructural protein 5 (NS5) of KV and MVEV were designed and used in single round PCRs to test for the respective viruses in infected cell cultures and, in the case of RRV, in samples of horse blood and synovial fluid. Results The primer pairs designed for each of the three viruses amplified a product of expected size from prototype viruses that were grown in cell culture. The identity of each of the products was confirmed by nucleotide sequencing indicating that in the context used the RT-PCRs were specific. RRV was detected in serums from 8 horses for which there were clinical signs consistent with RRV infection such that an acute-phase serum sample was taken and submitted for RRV serology testing. The RRV RT-PCR was analytically sensitive in that it was estimated to detect as little as 50 TCID50 of RRV per mL of serum and was specific in that the primer pairs did not amplify other products from the 8 serum samples. The RRV primers also detected virus in three independent mosquito pools known to contain RRV by virus isolation in cell culture. Samples from horses suspected to be infected with KV and MVEV were not available. Conclusion Despite much anecdotal and serological evidence for infection of horses with RRV actual infection and associated clinical disease are infrequently confirmed. The availability of a specific and analytically sensitive RT-PCR for the detection of RRV provides additional opportunities to confirm the presence of this virus in clinical samples. The RTPCR primers for the diagnosis of KV and MVEV infections were shown to be specific for cell culture grown viruses but the further validation of these tests requires the availability of appropriate clinical samples from infected horses.

Distribution of Sugarcane mosaic virus in sugarcane plants

Variation in the concentration of virus in different parts of the plant has implications for virus-indexing programs. To allow more reliable detection of Sugarcane mosaic virus (SCMV), the distribution of the virus in sugarcane plants after artificial inoculation was studied using a reverse transcription polymerase chain reaction (RT-PCR) assay. Leaves of susceptible and moderately resistant sugarcane were mechanically inoculated with SCMV 6 weeks after planting. Weekly for 8 weeks after inoculation, plants were examined for mosaic symptoms and samples of leaves, roots and tillers were tested by RT-PCR to detect virus. SCMV moved from the point of inoculation to younger leaves, roots and tillers and eventually to leaves that emerged prior to inoculation. The pattern of SCMV distribution in moderately resistant and susceptible cultivars was not substantially different. However, the virus moved more slowly in the moderately resistant than in the susceptible cultivar. Young leaves proved to be the most suitable tissue for testing.

Liver transplantation for HCV-associated liver cirrhosis: Predictors of outcomes in a population with significant genotype 3 and 4 distribution

End-stage liver disease associated with hepatitis C virus (HCV) infection is now the leading indication for liver transplantation in adults. However, reinfection of the graft is universal. We aimed to determine predictors of outcome of HCV-Iiver transplant recipients in the Australian and New Zealand communities. The following variables were analysed: demographic factors, coexistent pathology at the time of transplantation, HCV genotype, and donor age. Outcomes measures were: 1. mortality; 2. development of HCV-related complications, which were stage 3 or 4 fibrosis, or mortality from HCV-related graft failure, or both. Between January 1989 and December 30, 1999, 182 patients were transplanted for HCV-associated cirrhosis. The median follow-up period was 4 years (range, 0 to 13 years). Genotype data were available on 157 patients. The distribution of genotypes among the 157 patients was as follows: 36 (23%) genotype la, 30 (19%) genotype 1b, 4 (9%) genotype 1, 17 (11%) genotype 2, 41 (26%) genotype 3a, and 16 (10%) genotype 4. Eight (5%) patients were HCV-polymerase chain reaction (PCR)-negative (but HCV-antibody positive). Donor age and genotype 4 were associated with an increased risk of retransplantation or death (P < .001 and.05, respectively). Meanwhile, donor age, genotype 4, and pretransplant excess alcohol were risk factors for the development of HCV-related complications (P = .004, .008, and .02, respectively). In contrast, patients with genotype 3a were less likely to develop HCV-related complications (P = .05). In a population of HCV liver transplant recipients with a heterogeneous genotype distribution, donor age, and genotype 4, were predictors of a worse outcome, whereas genotype 3 was associated with a more favorable outcome.

Controlled Radical Polymerization of Styrene and Methyl Acrylate in the Presence of Reversible Addition-Fragmentation Chain Transfer Agents, Phenylethyl Phenyl Dithioacetate and Phenyldithioacetic Acid

The use of phenyldithioacetic acid (PDA) in homopolymerizations of styrene or methyl acrylate produced only a small fraction of chains with dithioester end groups. The polymerizations using 1-phenylentyl phenyldithioacetate (PEPDTA) and PDA in the same reaction showed that PDA had little or no influence on the rate or molecular weight distribution even when a 1:1 ratio is used. The mechanistic pathway for the polymerizations in the presence of PDA seemed to be different for each monomer. Styrene favors addition of styrene to PDA via a Markovnikov type addition to form a reactive RAFT agent. The polymer was shown by double detection SEC to contain dithioester end groups over the whole distribution. This polymer was then used in a chain extension experiment and the M-n was close to theory. A unique feature of this work was that PDA could be used to form a RAFT agent in situ by heating a mixture of styrene and PDA for 24 h at 70 degrees C and then polymerizing in the presence of AIBN to give a linear increase in Mn and low values of PDI (< 1.14). In the case of the polymerization of MA with PDA, the mechanism was proposed to be via degradative chain transfer. (c) 2005 Wiley Periodicals, Inc.

The distribution of Tannerella forsythia in an adolescent and adult population

Background: The fact that Tannerella forsythia, an important periopathogen, is difficult to cultivate from mixed infections has impeded precise estimates of its distribution within a given population. In order to discern T. forsythia alone from the mixed infection of plaque, the use of sensitive 16S ribosomal RNA based polymerase chain reaction (PCR) detection is necessary. Objectives: The aim of the present study was to determine the distribution of T. forsythia in an adult and in an adolescent population. Materials and methods: Subgingival plaque samples were obtained from 498 Australian adults and from 228 adolescent subjects from Manchester, UK. Tannerella forsythia was detected using PCR and confirmed by restriction analysis. Semi-quantitation of the organisms was carried out using two specific primers of differing sensitivities. Results: In the adolescent population, 25% were found to carry T. forsythia, albeit in relatively low numbers. In the adult population, a total of 37.8% and 11% were found to carry the organism with primer 2 and primer 1, respectively, suggesting that around 27% had between 10(3) and 10(7) organisms. Although there was an apparent increased proportion of T. forsythia positive subjects in those aged >= 50 years, this was not statistical significant. However, T. forsythia positive male smokers showed increased disease severity compared with T. forsythia negative subjects. Conclusion: This study has shown that at least 25% of the adolescent population carry low numbers of T. forsythia, whereas at least 37% of adults carry the organism, with some 11% having relatively high numbers. The relationship between T. forsythia and disease progression in these populations, however, remains to be determined.

Novel approach to tailoring molecular weight distribution and structure with a difunctional RAFT agent

This work has demonstrated that for the first time a single RAFT agent (i. e., difunctional) can be used in conjunction with a radical initiator to obtain a desired M-n and PDI with controlled rates of polymerization. Simulations were used not only to verify the model but also to provide us with a predictive tool to generate other MWDs. It was also shown that all the MWDs prepared in this work could be translated to higher molecular weights through chain extension experiments with little or no compromise in the control of end group functionality. The ratio of monofunctional to difunctional SdC(CH2Ph)S- end groups, XPX and XP (where X) S=C(CH2Ph) S-), can be controlled by simply changing the concentration of initiator, AIBN. Importantly, the amount of dead polymer is extremely low and fulfils the criterion as suggested by Szwarc (Nature 1956) that to meet living requirements nonfunctional polymeric species formed by side reactions in the process should be undetectable by analytical techniques. In addition, this novel methodology will allow the synthesis of AB, ABA, and statistical multiblock copolymers with predetermined ratios to be produced in a one-pot reaction.

Searching for convergence in phylogenetic Markov chain Monte Carlo

Markov chain Monte Carlo (MCMC) is a methodology that is gaining widespread use in the phylogenetics community and is central to phylogenetic software packages such as MrBayes. An important issue for users of MCMC methods is how to select appropriate values for adjustable parameters such as the length of the Markov chain or chains, the sampling density, the proposal mechanism, and, if Metropolis-coupled MCMC is being used, the number of heated chains and their temperatures. Although some parameter settings have been examined in detail in the literature, others are frequently chosen with more regard to computational time or personal experience with other data sets. Such choices may lead to inadequate sampling of tree space or an inefficient use of computational resources. We performed a detailed study of convergence and mixing for 70 randomly selected, putatively orthologous protein sets with different sizes and taxonomic compositions. Replicated runs from multiple random starting points permit a more rigorous assessment of convergence, and we developed two novel statistics, delta and epsilon, for this purpose. Although likelihood values invariably stabilized quickly, adequate sampling of the posterior distribution of tree topologies took considerably longer. Our results suggest that multimodality is common for data sets with 30 or more taxa and that this results in slow convergence and mixing. However, we also found that the pragmatic approach of combining data from several short, replicated runs into a metachain to estimate bipartition posterior probabilities provided good approximations, and that such estimates were no worse in approximating a reference posterior distribution than those obtained using a single long run of the same length as the metachain. Precision appears to be best when heated Markov chains have low temperatures, whereas chains with high temperatures appear to sample trees with high posterior probabilities only rarely. [Bayesian phylogenetic inference; heating parameter; Markov chain Monte Carlo; replicated chains.]