Long-term transients in a reactor under forced concentration cycling

In the approach to a cycle-invariant state in the forced feed concentration cycling of the CO oxidation over a NiO catalyst, a very long transient has been observed lasting 80 ks or more. This transient appears to be associated only with CO pretreatment of the catalyst and is not a general phenomenon. The slow convergence to the cycle-invariant state reported in certain modelling calculations in the literature appears to have a different cause.     

Retention of Escherichia coli in municipal sewage by means of planted soil filters in two-stage pilot plant systems.

Different types of constructed wetlands in a pilot-plant system were fed with identical municipal waste water to compare the sanitisation process in two-stage systems. With combinations of a vertical and a horizontal flow filter an E. coli reduction of 5 log10 with an E. coli influent concentration of 10(7) MPN/100 ml was achieved. Using different filter materials in each stage the total performance of the two-stage system was independent from the sequence of these materials. However, using coarser filter material in the first stage makes the filter less prone to clogging and is thus the preferential option with regard to operational reliability.     

Nanolayered lightweight flexible shields with multidirectional optical transparency

New nanolayered coatings are designed and deposited on flexible plastic substrate having the thickness of 100 /spl mu/m, in order to realize lightweight ultrathin transparent shielding foils. The structure of the coating is optimized considering three figures of merit: the average transmittance in the visible range for normal incidence, the normalized average transmittance for oblique incidence at 550 nm, and the transmittance quality factor. The nanotechnology exploited for the deposition of the transparent metals is the dual ion beam sputtering. Tests of durability, optical transmission, and shielding effectiveness demonstrate that the film has a high adhesion under mechanical solicitation, high resistance against aging, peak transmittance in the visible range higher than 70%, omnidirectional properties in the range 0/spl deg/-60/spl deg/, and shielding effectiveness of 40 dB up to 6 GHz.     

Contacting modes and behaviour classification of gas—solid and other two-phase suspensions

An attempt is made to extend schemes for classifying the behaviour of gas—solid contacting modes and other two-phase systems. The regime diagram approach of Reh (1971) is modified and extended to cover the operating regions of common reactors and contactors where a gas flows upwards through a bed of solids including fixed and moving packed beds, conventional fluidized beds, circulating beds, spouted beds, and pneumatically conveyed suspensions. New boundaries are proposed between groups A and B and between groups B and D of the Geldart (1972, 1973) powder classification scheme. These boundaries reflect more recent data and allow the classification scheme to be used for gases other than air and for temperatures and pressures other than atmospheric.     

Relationship between structure parameters and chemical properties in some MPS3 layered phases

Cationic thermal motions in the MPS₃ have been related to substitution abilities in this layer family. They have also been correlated to the crystal field stabilization energy. These considerations explain why some MPS₃ materials may or may not undergo a low temperature substitution intercalation reaction. From interatomic distances comparisons, the bond between (PS₃) groups in the anionic (P₂S₆)^4? octahedra, is found to be easily stretched upon cation substitution. Cationic radii follows the expected variation according to their high spin configuration in octahedral sulfur environment.     

Quantitative determination of aflatoxin B1 in chick liver

A method for the rapid and quantitative determination of aflatoxin B1 from small quantities of liver, around 1-2 g, is described. The extraction procedure involves acidification to pH 2 of the aqueous liver homogenates, extraction with chloroform: acetone and HPLC-fluorimetric detection after derivatization with trifluoroacetic acid. Quantitative recovery of aflatoxin B1 from chick liver was achieved and detection at levels of 0.2-1 ppb was proved feasible. The aflatoxin B1 concentration in chick liver after oral administration is also shown.     

Toughening of Dental Porcelain by Tetragonal ZrO2 Additions

The effect on mechanical behavior of ZrO₂ additions to a dental porcelain was investigated. The ZrO₂ was introduced into the glassy matrix phase of the porcelain by refritting the all-glass porcelain constituent. X-ray diffraction indicated that a sizeable fraction of the ZrO₂ was retained in the tetragonal form after the porcelain was fired. Zirconia additions to the porcelain produced substantial improvements in fracture toughness, strength, and thermal shock resistance.     

Elastic-Plastic Contact Damage in a Lead Lanthanum Zirconate Titanate

Spherical indenters were used to produce elastic-plastic contact damage in a lead lanthanum zirconate titanate (PLZT) under conditions of quasi-static and impact loading. The extent of radial cracking produced under both loading conditions showed good correlation with the response predicted by an earlier fracture mechanics analysis for quasi-static conditions. Calculated radial crack lengths corresponding to conditions of impact loading exhibited excellent agreement with experimentally measured values. The dynamic hardness of the PLZT was determined to be ∼ 1.5 times the quasi-static hardness. Differences in the radial crack lengths produced under the two loading conditions were attributed primarily to this difference in hardness response.     

Dissolution Profiling of Six Modified-Release Oral Solid Dosage Forms

Dissolution testing was conducted for six non-combination, single entity, modified-release oral solid dosage forms. Dissolution medium was water and 0.1 N hydrochloric acid. USP Apparatus 1 and Apparatus 2 were used arid were rotated at either 50 or 100 rpm. A complete dissolution profile was obtained for all six dosage forms based on their stated dosing interval, D. The three strengths of Theo-dur tablets, Norpace CR 150 mg capsules, and the two strengths of Chlor-trimeton tablets passed the Compendial Case One requirements (USP XXI, 2S, 1906). Thorazine spansules and Quinidex tablets were unable to meet the specifications with water as the dissolution medium; the latter showed improved dissolution character in 0.1 N hydrochloric acid. Tenuate Dospan 75 mg tablets showed good release characteristics in water when the authentic (dosing interval (D = 24 hours) was changed to a modified dosing interval of D* = 12 hours. All dissolution aliquots were assayed by UV absorbance measurements at the absorbance maximum for each drug and were also checked for excipient interference. Newer drugs appearing on the market will be more likely candidates for meeting compendial specifications; modified-release pharmaceuticals that appeared before the new specifications may have to be allocated specifically expanded window percentages.     

Dynamic viscosities of mixtures of n-butyraldehyde and isobutyraldehyde over wide ranges in the state parameters

Dynamic-viscosity measurements are reported for liquid mixtures in the system formed by n-butyraldehyde and isobutyraldehyde.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 321–322, February, 1985.