Letter: Differential Invariants of the Kerr Vacuum

The norms associated with the gradients of the two non-differential invariants of the Kerr vacuum are examined. Whereas both locally single out the horizons, their global behavior is more interesting. Both reflect the background angular momentum as the volume of space allowing a timelike gradient decreases with increasing angular momentum becoming zero in the degenerate and naked cases. These results extend directly to the Kerr-Newman geometry.     

Effect of crack tip sharpness on the strength of vulcanized rubbers

The effect of crack tip sharpness on crack propagation in vulcanized rubbers has been studied. For very sharp cracks, tearing is found to occur on a small scale at very low energies not far above the threshold required for the onset of mechanical crack growth. The “small-scale” tearing energies show relatively little variation for rubbers that differ widely in tear strength as normally measured. Thus the latter property appears to be strongly influenced by variations in the ability of rubbers to promote tip blunting. The small-scale tear behavior is of relevance to other fracture phenomena, including cutting by sharp objects and tensile failure. Natural variations in tip sharpness occur during cyclic or time-dependent mechanical crack growth and influence the form of the crack growth characteristics.     

The application of chromatography to the analysis of pharmaceutical creams

Summary The application of GLC, HPLC and TLC to the analysis of pharmaceutical creams is discussed with special attention to sample clean-up. The results of the determination of hydrocortisone acetate, salicylic acid, benzoic acid, diethyl stilbestrol, chloramphenicol, diphenhydramine HCl, tretinoin and some cream base components by reversed phase HPLC are given.Presented at the 14th International Symposium on Chromatography London, September, 1982     

The effect of the ammonium paratungstate source on the tungsten crystallite size

In an investigation into the effects of CaCl₂ on the sulfation of limestones in a laboratory furnace simulating fluidized-bed coal combustion conditions, small additions of CaCl₂ (<1 mole%) to the limestone prior to calcination were found to increase the extent of sulfation by changing the limestone pore structure. These changes were effected by trace amounts of liquid in the system in a synthetic SO₂/O₂ flue gas at 850°C. At much higher concentrations of CaCl₂, large amounts of a liquid phase are produced, containing a substantial quantity of dissolved CaO and leading to greatly enhanced sulfation when exposed to SO₂/O₂. The use of CaCl₂ additive in fluidized-bed combustion would reduce the quantity of limestones required to meet air pollution standards for SO₂ and also reduce the quantity of solid waste generated.     

Toward artificial developmental regulators

A polyamide-peptide conjugate is designed which recruits sequence specifically the developmental regulator Exd to a cognate DNA site. In particular, an eight-ring hairpin polyamide (Im-Im-Py(C3H6NHR)-Py-gamma-Im-Py-Py-Py-beta-Dp) with a heptapeptide (R = Ac-Phe-Tyr-Pro-Trp-Met-Lys-Gly-) attached on a central ring was shown to induce cooperative binding of the Drosophila Hox protein cofactor Exd with a Kd of 4.4 nM in vitro, an order of magnitude more efficient than the natural Hox protein partner Ubx. The conjugate joins two sequence specific domains, one for DNA and one for the protein. This small molecule thus serves as a cooperative protein-DNA dimerizer, which mimics the natural Hox family of developmental regulators.     

Sample preparation for high throughput accurate mass analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

An automated sample preparation for high throughput accurate mass determinations by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been developed. Sample preparation was performed with an automated workstation and automated mass analyses were performed with a commercial MALDI-TOF mass spectrometer. The method was tested with a 41-sample library. MALDI-TOFMS was found to give the needed sensitivity, accurate mass measurement, and soft ionization necessary for structure confirmation, even of mixtures. A mass accuracy of 5 ppm or less was obtained in over 80% of known compound measurements. A mass accuracy better than 10 ppm was obtained for all measurements of known compounds. Analyses of parallel synthesis products resulted in 77% of the measurements with a mass accuracy of 5 ppm or better.     

Remark concerning spherically symmetric nonstatic solutions to the Einstein equations in the comoving frame

All nonstatic spherically symmetric fluid solutions to the Einstein equations in the comoving frame $$ds^2 = e^{\lambda (r,t)} dr^2 + e^{\mu (r,t)} d\Omega ^2 - e^{v(r,t)} dt^2$$ are found subject to the conditions: (i) \(\dot \lambda = {\rm A}\dot \mu\) ,A = const, (ii) λ,μ, andν are separable functions ofr andt, (iii) the heat flux vanishes, and (iv) the coefficient of shear viscosity vanishes. There are but two classes of solutions: (i)A= 1, in which case the metric reduces to the Robertson-Walker form, and (ii)A=0, in which case there are four solutions, all with nonvanishing acceleration, expansion, and shear. WithA=0, the solutions are either singular at the origin or degenerate into spaces of constant curvature.     

Quantitative determination of sodium stearyl fumarate in a tablet formulation from continuous manufacturing using a high-pH reversed-phase HPLC method

This study demonstrates the first use of a reversed-phase (RP) high-performance liquid chromatography method with a high-pH buffer for the analysis of sodium stearyl fumarate (SSF) from a tablet formulation. After examining the retention time and peak shape using various buffer concentrations, buffer pH, and RP stationary phases, an optimized method was established using the XBridge® BEH C18 at high pH. This column was further evaluated for method specificity, accuracy, precision, linearity, stability, and sensitivity. Finally, the method was successfully used as a convenient and robust analytical procedure to accurately quantitate SSF in stratified tablets from a continuous manufacturing process to confirm the excipient uniformity throughout the process.