A thermal boundary control method for a flexible thin disk rotating over critical and supercritical speeds

In practice a rotating flexible thin annular disk has to be operated at low speed, because three types of dynamic instabilities inevitably occur around critical and supercritical speeds, namely: aeroelastic, parametric and thermoelastic. The rotating disk is clamped and driven by a drive shaft attached to the disk inner edge. The external action of the flowing surrounding air causes the aeroelastic instability; a slider mass-damper-spring-friction moving load causes parametric instability; and disk/slider interface friction heat can cause thermoelastic instability. A thermal boundary control method is used to induce disk thermal membrane stresses utilizing drive shaft temperature increments to stabilize these dynamic instabilities. Fundamental investigations are made of disk temperature distribution, thermal stress, natural frequency, dynamic stability and steady state amplitude to validate and demonstrate the viability of the new control method. The thermal boundary control method offers valuable opportunities for rotating disk applications operating over critical and supercritical high speeds with high efficiency

Methyl 9H-carbazole-9-acetate

The title compound, C15H13NO2, was synthesized by N-alkyl­ation of methyl bromo­acetate with 9H-carbazole. The carbazole ring system is essentially planar (mean atomic deviation = 0.0346 Å) and makes a dihedral angle of 86.5 (7)° with the methyl acetate group. Weak inter­molecular C—H⋯O hydrogen bonding is present in the crystal structure

(25R)-5a-Spiro­stane-3,12-dione

The title compound, C27H40O4, was obtained from the oxidation of (25R)-3b-hydr­oxy-5a-spiro­stan-12-one (Hecogenin) by Jone’s reagent. The mol­ecule contains six alicyclic and heterocyclic rings, all trans-fused, among which four six-membered rings adopt similar chair conformations while two five-membered rings assume an envelope conformation

2-(Carbazol-9-yl)acetic acid

In the title compound, C14H11NO2, the tricyclic aromatic ring system is essentially planar [maximum deviation = 0.025 (2) Å]. The dihedral angle between the two benzene rings is 2.8 (5)°, while the carboxyl group forms a dihedral angle of 88.5 (1)° with the pyrrole ring. Inter­molecular O—H⋯O hydrogen bonds may contribute to the overall stabilization of the crystal structure

2-Chloro­ethyl 4-nitro­benzoate

The title compound, C9H8ClNO4, crystallizes with two mol­ecules in the asymmetric unit. In each mol­ecule, the carboxyl­ate group is nearly coplanar with the benzene ring, forming dihedral angles of 2.4 (1) and 4.9 (1)°. In the crystal, mol­ecules are linked through weak C—H⋯O and C—H⋯Cl hydrogen bonds. A short O⋯N contact of 2.7660 (19) Å occurs between the nitro groups of adjacent mol­ecules

Dimethyl 5-nitro­isophthalate

The nitro group in the title compound, C10H9NO6, is rotated by 10.9 (5)° out of the plane of the benzene ring

5,6,7,8-Tetra­hydro­naphthalene-1-carboxylic acid

In the mol­ecule of the title compound, C11H12O2, the cyclo­hexane ring adopts a half-chair conformation. In the crystal structure, mol­ecules are linked into centrosymmetric dimers by pairs of O—H⋯O hydrogen bonds, and the dimers are linked together by π–π inter­actions [centroid–centroid distance = 3.8310 (13) Å] and C—H⋯O bonds

Seroprevalence of <em>Lawsonia intracellularis</em> antibodies in intensive pig farms in China

BACKGROUND: Porcine proliferative enteropathy caused by Lawsonia intracellularis (L. intracellularis) is a major concern to the pig industry worldwide. Although 8.3 billion pigs are produced each year in China, few reports on the prevalence of L.intracellularis infection are available. The aim of the current study was to estimate the seroprevalence of L. intracellularis antibodies in intensive pig farms in China. RESULTS: A total of 1060 serum samples were collected from 14 commercial pig farms located throughout China. Animals from all age groups were sampled including pre-weaning piglets, weaners, fattening pigs, adult sows and boars. Antibodies against L. intracellularis were detected using a specific blocking ELISA. Of the 1060 serum samples, 602 were identified as positive using the ELISA test. The apparent seroprevalence of L. intracellularis seropositivity was 57% (95% CI 50 to 64%). The true prevalence (that is, prevalence corrected for the imperfect sensitivity and specificity of the testing method) was 77% (95% CI 70 to 83%). CONCLUSIONS: The highest true prevalence was observed in sows and boars, suggesting that within a herd these stock classes are a reservoir for infection. The prevalence of L. intracellularis seropositivity in local breed pigs was significantly less than that in imported breeds. A higher seroprevalence was found in pigs in herds in Central and Northern China, which may correspond to the greater use of the intensive production systems in these areas. We conclude that L. intracellularis is widely prevalent in commercial pigs in China

Ethyl 4-chloro-3,5-dinitro­benzoate

In the title compound, C9H7ClN2O6, the nitro groups and the ester group make dihedral angles of 44.0 (1), 89.6 (1) and 164.1 (1)°, respectively, with the benzene ring. In the crystal, mol­ecules are linked through weak C—H⋯O hydrogen-bonding inter­actions. Mol­ecules are stacked via π–π inter­actions about inversion centers, with a centroid–centroid distance of 3.671 (2) Å