411 research outputs found
Zandaqa in the early Abbasid period with special reference to the poetry
SIGLEAvailable from British Library Document Supply Centre- DSC:D65139/86 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Effect of fluorination pattern and extent on the properties of PCDTBT derivatives
Herein, we report the synthesis of a series of fluorinated dithienyl carbazole-alt-benzothiadiazoles
(PCDTBT analogues) and the characterisation of their optical, electrochemical, thermal and molecular
organisation in the solid state. The polymers were decorated with fluorine on either the
benzothiadiazole unit, carbazole unit or both to yield PCDTffBT, PCffDTBT and PCffDTffBT, respectively.
The copolymers displayed decomposition temperatures in excess of 350 1C. PCDTffBT, PCffDTBT and
PCffDTffBT displayed optical band gaps of 1.86, 1.82 and 1.88 eV, respectively. It was speculated this
was a consequence of the higher molecular weight of PCffDTBT relative to the other polymers.
PCffDTBT and PCffDTffBT displayed shallower HOMO levels relative to PCDTffBT; a consequence of
fluorinating the carbazole-donor moiety. XRD studies confirmed that fluorinating the benzothiadiazoleacceptor
moiety improves molecular ordering by promoting p–p stacking of polymer backbones in solid
state. Interestingly, fluorinating the carbazole-donor unit does not improve p–p stacking of polymer
backbones
Pyrene- benzo[1,2,5]thiadiazole based conjugated polymers for application in BHJ solar cells
Ethylhexyloxy-functionalised pyrene (PEH) was prepared and copolymerised with both dithienyl-benzo[c]-[1], [2], [5]thiadiazole and dibithiophenyl-benzo[c]-[1], [2], [5]thiadiazole via a Stille coupling polymerisation method to yield PPEH-DTBT-8 and PPEH-DT2BT-8, respectively. A comparative study was conducted to assess the impact of substituting thiophene for bithiophene repeat units upon the resulting properties of the conjugated polymers. PPEH-DT2BT-8 which has bithiophene spacers between pyrene and benzothiadiazole repeat units, exhibited a narrower optical and electrochemical band gap relative to PPEH-DTBT-8; a consequence of the incorporating bithiophene spacer units which promote intramolecular charge transfer between the electron donating and electron accepting moieties. Both PPEH-DTBT-8 and PPEH-DT2BT-8 showed deep HOMO levels of -5.54 and -5.50 eV, respectively. The polymers possess good thermal stabilities with degradation temperatures in excess of 310 °C. The photovoltaic performance of the two polymers was studied by fabricating bulk heterojunction (BHJ) photovoltaic devices using PC70BM as the acceptor. PPEH-DTBT-8 and PPEH-DT2BT-8 demonstrated efficiencies of 0.33 and 1.83%, respectively. The higher efficiency of PPEH-DT2BT-8 can be attributed to vastly improved FF and Jsc values
Pyrene–benzothiadiazole-based copolymers for application in photovoltaic devices
The preparation and characterisation of four narrow band gap pyrene-benzothiadiazole based alternating copolymers is presented. An investigation of the impact of attaching different solubilising groups to the pyrene repeat units on the optical, electrochemical and thermal properties of the resulting materials was undertaken along with studies on the aggregation of polymer chains in the solid state. Unsurprisingly, polymers which had the smaller 2-ethylhexyl chains attached to the pyrene units (PPEH-DTBT and PPEH-DTffBT) displayed lower molecular weights relative to polymers with larger 2-hexyldecyl substituents (PPHD-DTBT and PPHD-DTffBT). Despite this, the 2-ethylhexyl substituted polymers displayed narrower optical band gaps relative to their analogous 2-hexyldecyl substituted polymers. Of all polymers synthesised, PPEH-DTBT displayed the lowest optical band gap (1.76 eV) in the series. All polymers display degradation temperatures in excess of 300°C. Polymers with smaller alkyl chains on the pyrene units display shallower HOMO levels which could be due to increased intramolecular charge transfer between the donor and acceptor units. Preliminary investigations on bulk heterojunction solar cells with a device structure ITO/PEDOT:PSS/Polymer:PC70BM/Ca/Al were undertaken. Polymer/PC70BM blend ratios of 1/3 were used in these studies and have indicated that PPEH-DTBT displayed the highest efficiency with a PCE of 1.86 %
Mapping genetic determinants of host susceptibility to Pseudomonas aeruginosa lung infection in mice.
Background: P. aeruginosa is one of the top three causes of opportunistic human bacterial infections. The remarkable
variability in the clinical outcomes of this infection is thought to be associated with genetic predisposition. However,
the genes underlying host susceptibility to P. aeruginosa infection are still largely unknown.
Results: As a step towards mapping these genes, we applied a genome wide linkage analysis approach to a mouse
model. A large F2 intercross population, obtained by mating P. aeruginosa-resistant C3H/HeOuJ, and susceptible A/J
mice, was used for quantitative trait locus (QTL) mapping. The F2 progenies were challenged with a P. aeruginosa
clinical strain and monitored for the survival time up to 7 days post-infection, as a disease phenotype associated trait.
Selected phenotypic extremes of the F2 distribution were genotyped with high-density single nucleotide polymorphic
(SNP) markers, and subsequently QTL analysis was performed. A significant locus was mapped on chromosome 6 and
was named P. aeruginosa infection resistance locus 1 (Pairl1). The most promising candidate genes, including Dok1,
Tacr1, Cd207, Clec4f, Gp9, Gata2, Foxp1, are related to pathogen sensing, neutrophils and macrophages recruitment and
inflammatory processes.
Conclusions: We propose a set of genes involved in the pathogenesis of P. aeruginosa infection that may be explored
to complement human studie
Thermally stable solution processed vanadium oxide as a hole extraction layer in organic solar cells
Low-temperature solution-processable vanadium oxide (V2Ox) thin films have been employed as hole extraction layers (HELs) in polymer bulk heterojunction solar cells. V2Ox films were fabricated in air by spin-coating vanadium(V) oxytriisopropoxide (s-V2Ox) at room temperature without the need for further thermal annealing. The deposited vanadium(V) oxytriisopropoxide film undergoes hydrolysis in air, converting to V2Ox with optical and electronic properties comparable to vacuum-deposited V2O5. When s-V2Ox thin films were annealed in air at temperatures of 100 °C and 200 °C, OPV devices showed similar results with good thermal stability and better light transparency. Annealing at 300 °C and 400 °C resulted in a power conversion efficiency (PCE) of 5% with a decrement approximately 15% lower than that of unannealed films; this is due to the relative decrease in the shunt resistance (Rsh) and an increase in the series resistance (Rs) related to changes in the oxidation state of vanadium
Polymorphic characterisation of gallinacin candidate genes and their molecular associations with growth and immunity traits in chickens
1.Four gallinacin (GAL) genes were assessed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) to characterise these genes in Fayoumi (F) and Rhode Island Red (R) breeds and their crosses of Rhode Island Red × Fayoumi (½R½F) and Fayoumi × Rhode Island Red (½F½R). 2.Genes examined were GAL2, GAL3, GAL4 and GAL5. The molecular associations between the SNPs of the gallinacin genes and body weight, caecal bacterial count and the serum antibody titres of IgA, IgG and IgM were determined. In the R breed, the frequency of TC genotype was higher than TT and CC genotypes for the GAL3 gene. The GG genotype frequency was higher than AA and AG genotypes for the GAL4 gene in the other genetic groups, and the CA genotype frequency was higher than CC and AA genotypes in crosses for the GAL5 gene. 3.In all populations, the frequency of the C allele was higher than the T allele for the GAL3 gene, the G allele was higher than the A allele for the GAL4 gene and the C allele was higher than the A allele for the GAL5 gene. The observed heterozygosity in R, ½R½F and ½F½R was 0.476, 0.375 and 0.158 for the GAL3 gene, 0.458, 0.615 and 0.250 for the GAL4 gene and 0.053, 0.792 and 0.739 for the GAL5 gene, while the expected heterozygosities were 0.490, 0.430 and 0.145 for the GAL3 gene, 0.430, 0.348 and 0.219 for the GAL4 gene and 0.229, 0.478 and 0.496 for the GAL5 gene, respectively. 4.On a molecular level, the genotype TT was significantly higher for body weight than TC and CC genotypes in the GAL3 gene. Birds with the GG genotype had a significantly lower Salmonella typhimurium count than birds with AA genotype in the GAL4 gene. Birds with the genotype AA had higher significant body weights than those with CC and CA genotypes in the GAL5 gene. 5.The results indicated that the GAL3, GAL4 and GAL5 genes are potential candidates for selection programmes to improve S. typhimurium resistance and body weight in chickens
Development of an efficient regeneration system for bombarded calli from immature embryos of Moroccan durum wheat varieties
ArticleOne of the biggest obstacles limiting genetic transformation of durum wheat is the lack
of an efficient regeneration system for bombarded tissues. Our study aims to optimize culture
conditions for regenerating bombarded calli from immature embryos of four durum wheat
varieties ‘Amria’, ‘Chaoui’, ‘Isly’ and ‘Marouane’, through comparing the effects of
phytohormones (IAA, zeatin and their interaction) and nitrogen amount and sources on callus
induction and plant regeneration. Both tested induction media induced approximately the same
rate of induced calli for all the tested varieties. However, the interaction of the induction and the
regeneration media showed a highly significant effect on plantlet regeneration for all tested
varieties. After bombardment, IM1/RM2 combination proved to be the favourable medium with
up to 200% and 120% plantlets regenerated for ‘Chaoui’ and ‘Isly’ varieties respectively.
Encouraging results obtained in this study will help to promote the research in genetic
transformation and its improvement
Genetic mapping of novel modifiers for ApcMin induced intestinal polyps’ development using the genetic architecture power of the collaborative cross mice
Background: Familial adenomatous polyposis is an inherited genetic disease, characterized by colorectal polyps. It is caused by inactivating mutations in the Adenomatous polyposis coli (Apc) gene. Mice carrying a nonsense mutation in the Apc gene at R850, which is designated ApcMin/+ (Multiple intestinal neoplasia), develop intestinal adenomas. Several genetic modifier loci of Min (Mom) were previously mapped, but so far, most of the underlying genes have not been identified. To identify novel modifier loci associated with ApcMin/+, we performed quantitative trait loci (QTL) analysis for polyp development using 49 F1 crosses between different Collaborative Cross (CC) lines and C57BL/6 J-ApcMin/+mice. The CC population is a genetic reference panel of recombinant inbred lines, each line independently descended from eight genetically diverse founder strains. C57BL/6 J-ApcMin/+ males were mated with females from 49 CC lines. F1 offspring were terminated at 23 weeks and polyp counts from three sub-regions (SB1–3) of small intestinal and colon were recorded.
Results: The number of polyps in all these sub-regions and colon varied significantly between the different CC lines. At 95% genome-wide significance, we mapped nine novel QTL for variation in polyp number, with distinct QTL associated with each intestinal sub-region. QTL confidence intervals varied in width between 2.63–17.79 Mb. We extracted all genes in the mapped QTL at 90 and 95% CI levels using the BioInfoMiner online platform to extract, significantly enriched pathways and key linker genes, that act as regulatory and orchestrators of the phenotypic landscape associated with the ApcMin/+ mutation.
Conclusions: Genomic structure of the CC lines has allowed us to identify novel modifiers and confirmed some of the previously mapped modifiers. Key genes involved mainly in metabolic and immunological processes were identified. Future steps in this analysis will be to identify regulatory elements – and possible epistatic effects – located in the mapped QTL
Polymer-based solar cells having an active area of 1.6 cm2 fabricated via spray coating
We demonstrate the fabrication of polymersolar cells in which both a PEDOT:PSS hole transport and a PCDTBT:PC71BM photoactive layer are deposited by spray-casting. Two device geometries are explored, with devices having a pixel area of 165 mm2 attaining a power conversion efficiency of 3.7%. Surface metrology indicates that the PEDOT:PSS and PCDTBT:PC71BM layers have a roughness of 2.57 nm and 1.18 nm over an area of 100 μm2. Light beam induced current mapping reveals fluctuations in current generation efficiency over length-scales of ∼2 mm, with the average photocurrent being 75% of its maximum value
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