Poly(arylene ether sulphones) by polyetherification: 1. Synthesis of halogenophenols

Several 4-halogenophenylsulphonylphenols, useful as intermediates for the synthesis of poly(arylene ether sulphones), have been prepared by partial hydrolysis of the corresponding dihalides and/or by the reaction of 4-halogenoarylsulphonyl chlorides with diaryl carbonates under Friedel—Crafts conditions followed by hydrolysis of the sulphonylated carbonates. The novel reagent, diphenyl carbonate-4,4′-disulphonyl chloride, has been prepared by chlorosulphonylation of diphenyl carbonate and used to introduce the 4-hydroxyphenylsulphonyl group into aryl halides, thus providing a third general route to the halogeno phenols. 4-Fluoro-3′-hydroxydiphenyl sulphone and the 4-fluoro-2′-hydroxy derivative have been synthesised by classical procedures.     

Effect of initial breeding weight and management system using a high-producing sow genotype on resulting reproductive performance over three parities

A study was conducted with sows of a high-producing genotype to evaluate their reproductive performance using three breeding weights over a three-parity period in two management systems. A total of 114 F1 gilts (Landrace x Yorkshire) were used in a split-plot, randomized, complete block experiment conducted as a 3 x 2 factorial arrangement of treatments in two replicates. Three gilt breeding weights of 120, 135, and 150 kg were achieved by feeding 1.8, 2.3, or 3.2 kg/d of a .73% lysine corn-soybean meal (C-SBM) diet, respectively, from 5 to 8 mo of age. Two locations, each with different management systems, were considered the main plot and consisted of 1) outside, concrete-floored gestation lots and indoor farrowing pens or 2) indoor gestation pens and farrowing crates. All sows were fed 1.8 (Parity 1) or 2.1 (Parity 2 and 3) kg/d of a .73% lysine C-SBM diet during the breeding and gestation periods, whereas a .82% lysine C-SBM diet with 5% added fat was available ad libitum during lactation. All sows lost weight during the first lactation; larger weight losses occurred as breeding weight increased (P < .01). During the second and third lactations the 135- and 150-kg sow breeding groups had less lactation weight change, whereas the 120-kg group lost more weight, resulting in a breeding weight x parity interaction (P < .01). The 120-kg breeding weight group consumed less feed (P < .05) for the three lactation periods than did the heavier weight groups. Initial breeding weight had no effect on number of pigs born (total, live) or pig and litter weights at birth. Pig mortality increased with increasing breeding weight (P < .01) and parity (P < .05), a response that was exacerbated when sows farrowed in pens vs crates. Postweaning breeding intervals and sow removal from the experiment were not significantly affected by initial breeding weight, but a numerically higher percentage of sows in the 120-kg group were anestrous or failed to conceive than the percentage of such sows in the heavier weight groups. These data suggest that an initial breeding weight of approximately 135 kg at 8 mo of age may be best when sows farrow in crates, whereas when sows farrow in pens a lower breeding weight may be more desirable.     

Double mutagenesis of a positive charge cluster in the ligand-binding site of the ferric enterobactin receptor, FepA

Siderophores and colicins enter bacterial cells through TonB-dependent outer membrane proteins. Using site-directed substitution mutagenesis, we studied ligand recognition by a prototypic Escherichia coli siderophore receptor, FepA, that binds the iron chelate ferric enterobactin and colicins B and D. These genetic experiments identified a common binding site for two of the three ligands, containing multiple positive charges, within cell surface residues of FepA. Elimination of single residues in this region did not impair the adsorption or transport of ferric enterobactin, but double mutagenesis in the charge cluster identified amino acids (Arg-286 and Arg-316) that participate in siderophore binding and function in FepA-mediated killing by colicins B and D. Ferric enterobactin binding, furthermore, prevented covalent modification of FepA within this domain by either a fluorescent probe or an arginine-specific reagent, corroborating the involvement of this site in ligand recognition. These results identify, for the first time, residues in a TonB-dependent outer membrane protein that participate in ligand binding. They also explain the competition between ferric enterobactin and the colicins on the bacterial cell surface: all three ligands interact with the same arginine residues within FepA during their penetration through the outer membrane.     

A rate gyroscope based on interaction of sonic waves

A new form of rate gyroscope based on interaction between standing sonic waves in solid media is described. One form of the device, using a solid, ring-shaped medium, is analyzed in order to establish the relationship between the modes of the two waves that must exist to produce sensitivity to angular rate. In addition, the analysis establishes estimates for the angular-rate sensitivity in terms of the basic instrument parameters. The theoretical feasibility of the proposed instrument has been confirmed by experiments conducted on a simple laboratory model. The results indicate that strain-induced and mass unbalance cross-coupling between the driving and sensing waves can produce uncertainty in the instrument output signal. These unwanted cross-coupling effects are the practical limitation on the instrument performance at the present time. Methods for their reduction and cancellation are discussed for the ring-shaped transducer. The problem of unwanted cross-coupling seems to be present in sonic gyroscopes, in general, and is not unique to solid media alone. In particular, some preliminary experiments with fluid devices show them to have similar cross-coupling problems. In conclusion, the major advantages over conventional rate gyroscopes of instruments based on interaction of sonic waves appear to be: low power consumption, long life, (potentially) high reliability, ruggedness, and low cost. These advantages must be weighed against the primary disadvantage of the lower precision that is available at the present state of the development.     

Suspected bacterial meningoencephalitis in two adult horses

Bacterial infections (such as meningitis or meningoencephalitis) of the central nervous system are rare in horses. They are most prevalent in neonates as a result of septicaemia. A few cases have been reported in the adult and most have been fatal. Streptococcal species appear to be the organism most commonly identified in these cases. Thus, this disease may be a secondary complication of upper respiratory tract infections. Clinical signs are extremely variable making diagnosis difficult. In most cases, postmortem has been the definite diagnostic procedure. This paper describes the clinical course of disease, diagnosis and successful treatment of two presumptive cases of meningoencephalitis in adult horses.     

Evidence for multiple substrate-reduction sites and distinct inhibitor-binding sites from an altered Azotobacter vinelandii nitrogenase MoFe protein

The arginine-277 residue of the alpha-subunit of the nitrogenase MoFe protein was targeted for substitution because it is (i) a close neighbor of alpha-cysteine-275, which is one of only two residues anchoring the FeMo cofactor to the polypeptide, and (ii) a component of a potential channel for entry/exit of substrates/products and for accepting FeMo cofactor during MoFe-protein maturation. Several of the eight mutant strains constructed were capable of good diazotrophic growth and also contained FeMo cofactor as indicated by its biologically unique S = 3/2 EPR spectrum. These observations indicate that the positively charged alpha-arginine-277 residue is not required for acceptance of the negatively charged FeMo cofactor by the separately synthesized, cofactor-deficient, apo-MoFe protein. The wide range of nitrogen-fixation phenotypes shown by these mutant strains generally correlated well with their C2H2- and proton-reduction activities, which range from 5 to 65% of wild-type activity. One notable exception is the histidine-substituted strain, DJ788 (alpha-277His). This strain, although unable to fix N2 and grow diazotrophically, elaborates an altered alpha-277His MoFe protein that catalyzes the reduction of the alternative substrates, C2H2, HCN, HN3, and protons. These observations are best explained if multiple redox levels are available to the MoFe protein but the alpha-277His MoFe protein is incapable of reaching the more-reduced redox levels required for nitrogen fixation. Under nonsaturating CO concentrations, the alpha-277His MoFe-protein-catalyzed reduction of C2H2 showed sigmoidal kinetics, which is consistent with inhibitor-induced cooperativity among two C2H4-evolving sites and indicates the presence of three sites, which can be simultaneously occupied, on the MoFe protein. Similar kinetics were not observed for alpha-277His MoFe-protein-catalyzed reduction of either HCN or HN3 with nonsaturating CO levels, indicating that these substrates are unlikely to share common binding sites with C2H2. Further, CN- did not induce cooperativity in C2H2 reduction and, therefore, CO and CN- are unlikely to share a common binding site. These changed substrate specificities, reinforced by changes in the FeMo-cofactor-derived S = 3/2 EPR spectrum, clearly indicate the importance of the alpha-277 residue in catalysis and the delicate control exerted on the properties of bound FeMo cofactor by its polypeptide environment.     

Transducer and multistrip-coupler performance for leaky surface waves on lithium niobate

Measurements are reported of the properties of leaky surface waves propagating on 41° and 64° rotated cuts of LiNbO3 both on the free surface and under metal. Transducer and multistrip-coupler performance are consistent with piezo electric-coupling constants of 18° and 12%, respectively. Insertion-loss and spurious-signal-level results show that the interdigital transducer with few finger pairs is better matched to a metallised propagation path than to a free surface path for leaky waves.