Rotational symmetry of a methane molecule and the bond angle

The rotational symmetry of a methane molecule can be used to great advantage to calculate the bond angle. The problem is worked out in this article.

The development of a ligase mediated PCR with potential for the differentiation of serovars within Leptospira interrogans

A ligase mediated polymerase chain reaction (LMPCR) was developed to amplify between the repetitive element, IS1533, of Leptospira and adjacent chromosomally located BglII restriction endonuclease enzyme sites. To do this, complimentary oligonucleotide linkers designed to anneal together with an overhanging BglII end were ligated to BglII digested DNA from 35 leptospiral reference strains and field isolates, This ligated DNA was used as template for PCR with oligonucleotide primers specific for the linker and for the repetitive element IS1533. The resultant amplicon profile hybridised a 102 hp region derived from the terminus of IS1533 thus confirming that amplicons generated by LMPCR contained part of IS1533. The number of fragments generated containing IS1533 was significantly fewer than that generated by RFLP but the LMPCR method has the potential to use far less template DNA and be quicker than standard RFLP. Obvious and reproducible interserovar differences were demonstrated by LMPCR whereas for 20 of 21 L. hardjo-bovis isolates tested no intraserovar differences were observed. Of those serovars known to possess IS1533 homologues and tested here by LMPCR, each produced a unique amplicon profile which hybridised the IS1533 terminus probe. The limited heterogeneity amongst hardjo-bovis isolates is discussed as is the potential contribution of this method to diagnosis, differentiation and the phylogenetics of the Leptospires.

The role of fimbriae and flagella in the colonization, invasion and persistence of Escherichia coli O78 : K80 in the day-old-chick model

To understand the role of flagella and fimbriae of Escherichia coli O78:K80 in avian colibacillosis, day-old chicks were dosed orally with defined afimbriate and or aflagellate mutants and colonization, invasion and persistence compared with that of the wild-type. In an invasion model, chicks were dosed with 1 x 10(5) c.f.u. of a single strain and mutants defective for type 1 fimbriae, curli fimbriae or flagella colonized livers by 24 h although the numbers of bacteria present were significantly less than the wild-type, Mutants colonized between 50 and 75 % of spleens whereas the wild-type colonized 100 % of spleens. Additionally, the numbers of mutant bacteria in colonized spleens were significantly less than the wild-type. Surprisingly, mutants defective for the elaboration of more than one appendage were no more attenuated than single mutants. In a persistence model, chicks were dosed with 1 x 10(2) c.f.u. of a single strain and mutants defective for type 1 or curli or flagella or any combination thereof persisted as assessed by cloacal swabbing for 5 weeks of the experiment less well than the wild-type. In an additional persistence model, chicks were dosed with 5 x 10(2) c.f.u. of each of wild-type and one mutant together. All mutants were significantly less persistent than the wild-type (P < 0.001) and one mutant which lacked type 1, curli and flagella, was eliminated within 2 weeks. Analysis of the trends of elimination indicated that flagella contributed to persistence more than curli, which contributed more than type 1 fimbriae. Here was evidence for a major role in colonization, invasion and persistence played by type 1, curli and flagella.

p90 ribosomal S6 kinases play a significant role in early gene regulation in the cardiomyocyte response to Gq protein-coupled receptor stimuli, endothelin-1 and α1-adrenergic receptor agonists

Extracellular signal-regulated kinases 1/2 (ERK1/2) and their substrates, p90 ribosomal S6 kinases (RSKs), phosphorylate different transcription factors, contributing differentially to transcriptomic profiles. In cardiomyocytes, ERK1/2 are required for >70% of the transcriptomic response to endothelin-1. Here, we investigated the role of RSKs in the transcriptomic responses to Gq protein-coupled receptor agonists, endothelin-1, phenylephrine (generic α1-adrenergic receptor agonist) and A61603 (α1A-adrenergic receptor selective). Phospho-ERK1/2 and phospho-RSKs appeared in cardiomyocyte nuclei within 2-3 min of stimulation (endothelin-1>a61603≈phenylephrine). All agonists increased nuclear RSK2, but only endothelin-1 increased nuclear RSK1 content. PD184352 (inhibits ERK1/2 activation) and BI-D1870 (inhibits RSKs) were used to dissect the contribution of RSKs to the endothelin-1-responsive transcriptome. Of 213 RNAs upregulated at 1 h, 51% required RSKs for upregulation whereas 29% required ERK1/2 but not RSKs. The transcriptomic response to phenylephrine overlapped with, but was not identical to, endothelin-1. As with endothelin-1, PD184352 inhibited upregulation of most phenylephrine-responsive transcripts, but the greater variation in effects of BI-D1870 suggests that differential RSK signalling influences global gene expression. A61603 induced similar changes in RNA expression in cardiomyocytes as phenylephrine, indicating that the signal was mediated largely through α1A-adrenergic receptors. A61603 also increased expression of immediate early genes in perfused adult rat hearts and, as in cardiomyocytes, upregulation of the majority of genes was inhibited by PD184352. PD184352 or BI-D1870 prevented the increased surface area induced by endothelin-1 in cardiomyocytes. Thus, RSKs play a significant role in regulating cardiomyocyte gene expression and hypertrophy in response to Gq protein-coupled receptor stimulation.

Conductance and relaxations of gelatin films in the glassy and rubbery states

The dielectric constant, epsilon', and the dielectric loss, epsilon'', for gelatin films were measured in the glassy and rubbery states over a frequency range from 20 Hz to 10 MHz; epsilon' and epsilon'' were transformed into M* formalism (M* = 1/(epsilon' - i epsilon'') = M' + iM''; i, the imaginary unit). The peak of epsilon'' was masked probably due to dc conduction, but the peak of M'', e.g. the conductivity relaxation, for the gelatin used was observed. By fitting the M'' data to the Havriliak-Negami type equation, the relaxation time, tauHN, was evaluated. The value of the activation energy, Etau, evaluated from an Arrhenius plot of 1/tauHN, agreed well with that of Esigma evaluated from the DC conductivity sigma0 both in the glassy and rubbery states, indicating that the conductivity relaxation observed for the gelatin films was ascribed to ionic conduction. The value of the activation energy in the glassy state was larger than that in the rubbery state.

Emission: a simple new technique to correct rainfall estimates from attenuation due to both the radome and heavy rainfall

We present a new technique for correcting errors in radar estimates of rainfall due to attenuation which is based on the fact that any attenuating target will itself emit, and that this emission can be detected by the increased noise level in the radar receiver. The technique is being installed on the UK operational network, and for the first time, allows radome attenuation to be monitored using the increased noise at the higher beam elevations. This attenuation has a large azimuthal dependence but for an old radome can be up to 4 dB for rainfall rates of just 2–4 mm/h. This effect has been neglected in the past, but may be responsible for significant errors in rainfall estimates and in radar calibrations using gauges. The extra noise at low radar elevations provides an estimate of the total path integrated attenuation of nearby storms; this total attenuation can then be used as a constraint for gate-by-gate or polarimetric correction algorithms.