Calculation of skin permeability coefficient for ionized and unionized species of indomethacin.

The contribution of ionized and unionized species to the overall permeation of weak electrolytes through the skin was investigated to determine the effect of pH in the vehicle on the permeability of indomethacin (IDM), as a model drug, through hairless rat skin. The permeability of IDM through polydimethylsiloxane (silicone) and poly(2-hydroxyethyl methacrylate) (pHEMA) membranes which may reflect lipid and aqueous pathway, respectively, was also measured for comparison. As the pH in the vehicle increased, there was an exponential increase in the skin permeation rate of IDM. The permeation rate of IDM through the silicone membrane was constant independent of pH, whereas that through the pHEMA membrane increased with increasing pH, similar to the skin permeation. The permeability coefficients of ionized and unionized species through the skin estimated using the skin permeation rates and solubilities of IDM at various pHs were 1.50 x 10(-7) and 2.79 x 10(-5) cm/s, respectively. These results indicated that the permeation of ionized species greatly contributed to the total permeation of IDM at higher pH, and that the total permeation rate of IDM was determined by the permeation of unionized species at lower pH. These contributions depend on the pH and pKa values and the ratio of permeability coefficient of each species. It was also confirmed that the skin has at least two kinds of permeation pathways and these two species permeate through a different pathway.     

Wirkungsgrade in der Welt des Lebens und der Technik

Zusammenfassung Um der oft gehörten Meinung entgegenzutreten, die energetischen Wirkungsgrade lebender Organismen seien wesentlich höher als die technischer Verfahren, werden entsprechende Werte miteinander verglichen. Der sehr niedrige Wirkungsgrad der Photosynthese zusammen mit der kleinen Energiedichte der Sonnenstrahlung erzwang ab einer kritischen Größe die Aufspaltung in Energiesammler, die Pflanzen, und Verbraucher chemischer Energie, den Tieren. Dank den 10 mal höheren Wirkungsgraden in der Technik, lassen sich Solarmobile bauen, die von der auf sie fallenden Sonnenstrahlung angetrieben werden. Wegen des Multiplikationsgesetzes der Teilwirkungsgrade ergeben sich sowohl für die Speicherung der Sonnenenergie in den fossilen Brennstoffen wie in der Nahrungskette extrem niedrige Wirkungsgrade.

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Efficiencies in the world of life and in engineering

One often hears the opinion, that the efficiencies in the world of life are higher than in engineering. To disprove this, many values of efficiency of corresponding processes are compared. The very low efficiency of photosynthesis in living plants together with the low density of solar radiation has led the world of life to split into collectors of energy, the plants, and consumers of chemical energy, the animals. Thanks to the ten times higher efficiencies of solar cells, it is possible, to produce solar mobiles, vehicles that move driven by solar radiation.

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Herrn Prof. Dr.-Ing. U. Grigull zum 75. Geburtstag gewidmet     

Pore Structure Analysis of Porous Particles by Equivalent Model

Starting from Wheeler's composite theory, which takes both the multilayer adsorption and the capillary condensation into consideration, and assuming the equivalent cylindrical model, we have deduced a strict and relatively simpler formula for the calculation of pore size distribution by solving the integral equation directly. The formula is more convenient for application because of its recursion form. Following the same line of reasoning and using the mean value theorem of definite integrals under different conditions, we have unified the equations of Barrett-Joyner-Halenda, Dubinin, Cranston-Inkley, Dollimore-Heal and Roberts. A table of parameters which is required in the calculation is given. Besides the adsorption of nitrogen, the adsorption with water vapor as the adsorbate is investigated and the corresponding empirical equation of adsorption thickness is given.     

Umsetzung von hydrobromiertem 1,4-Polybutadien mit lithiumorganischen Verbindungen

Ohne ZusammenfassungMit 1 Abbildung und 1 Tabelle     

Die Schmelzdiagramme der Systeme CsN3/Zn(N3)2 und KN3/Zn(N3)2

The phase diagrams of the systems CsN₃/Zn(N₃)₂ and KN₃/Zn(N₃)₂ have been obtained employing the microscopic technique ofL. Kofler andA. Kofler. Within the system CsN₃/Zn(N₃)₂ three eutectics at 148°C, 142°C, and 210°C were found. Besides Cs₂Zn(N₃)₄, melting incongruently in the interval 153°C to 170°C, there exist two further compounds of the most probable composition Cs₃Zn₂(N₃)₇ and CsZn₂(N₃)₅, melting congruently at 170°C and 210°C, resp. In the system KN₃/Zn(N₃)₂ there exist two eutectics at 203°C and 172°C and two compounds, one of them, i.e. K₂Zn(N₃)₄, melting congruently at 206°C, the other one, with composition KZn₃(N₃)₇ or KZn₄(N₃)₉, melting incongruently at 210°C.

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Mit 8 Abbildungen

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Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet.     

Vernetzung und Abbau von Polyäthylenterephthalat durch Elektronenbestrahlung

Zusammenfassung PÄT-Folien wurden in Luft, Stickstoff und Vakuum bei 20 °C mit 1 MeV-Elektronen bestrahlt. Untersucht wurden Löslichkeit und Viskosität von Proben, die unmittelbar nach der Bestrahlung gelöst wurden.In allen untersuchten Fällen trat bei hohen Bestrahlungsdosen ein unlöslicher, d. h. vernetzter Anteil auf, dessen Ausbildung jedoch durch in den Proben enthaltene Feuchtigkeit verzögert werden kann. Bei niedrigen Bestrahlungsdosen bewirkt Feuchtigkeit einen Abbau des Polymeren, wie durch Viskositätsmessungen gezeigt wird.Aus den Gel-Messungen wurde derp ₀/q ₀-Wert für Bestrahlung in Luft, Stickstoff und Vakuum zu 1,05 bestimmt.Die Änderung des Gel-Anteils bei Lagerung der Proben zwischen Bestrahlung und Lösung wird diskutiert.

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Summary Polyethyleneterephthalate samples were irradiated in air, nitrogen and vacuum at 20 °C with 1 MeV electrons. The solubility of the samples and the viscosity of the solutions were studied immediately after irradiation. At high doses an insoluble crosslinked part was always observed. Crosslinking was delayed by moisture in the samples. At low irradiation doses moisture causes chain scission as shown by viscosity measurements. The ratiop ₀/q ₀ of degradation to crosslinking in the case of irradiation in air, nitrogen and vacuum was found by gel measurements to be 1.05. The insoluble gel-part changes with increasing storage time of the samples between irradiation and solution.

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Herrn Diplom-PhysikerH. Fischer sei an dieser Stelle für wertvolle Anregungen und Diskussionen besonders gedankt.     

Viskoelastische Eigenschaften von Polyisobutylenen in verdünnten Lösungen

Zusammenfassung Die Speicher- und VerlustmodulnG undG verdünnter Lösungen (2–4%) dreier Isobutylenpolymerisate mit den Molekulargewichten 0,63, 1,29 und 11×10⁵ wurden in der Apparatur vonBirnboim undFerry über einen Frequenzbereich von 0,4–400 Hz und einen Temperaturbereich von –17,5 bis 25,0° bestimmt. Für die scharf fraktionierten Polymerisate von niederem Molekulargewicht ergab die Frequenzabhängigkeit der Moduln eine ausgezeichnete Übereinstimmung mit der Theorie vonZimm. Die aus den experimentell erhaltenen Kurven ermittelten Molekulargewichte und größten Relaxationszeiten waren von der erwarteten Größenordnung. Für das Polymerisat mit höherem Molekulargewicht entsprach die Frequenzabhängigkeit vonG undG – _s jedoch der Theorie vonRouse. Der Einfluß der hydrodynamischen Wechselwirkung in der Bewegung der Knäuelsegmente, in welchem der Unterschied zwischen den beiden Theorien besteht, erscheint als von der Größe des Molekulargewichts abhängig.

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Summary The storage and loss moduliG andG of dilute (2–4%) solutions of three polyisobutylenes of molecular weight 0.63, 1.29, and 11×10⁵ were determined in the apparatus ofBirnboim andFerry over a frequency range of 0.4 to 400 cps, and a temperature range of –17.0 to 25.0°. The sharply fractionated polymers of low molecular weight showed a frequency dependence in excellent agreement with the theory ofZimm. The experimentally determined molecular weights and terminal relaxation times were of the expected order of magnitude. The frequency dependence of the polymer of highest molecular weight, however, conformed more closely to the theory ofRouse. The influence of the hydrodynamic interaction on the motion of the coil segments, which constitutes the difference in the two theories, appears to depend on the magnitude of the molecular weight.

     

Chiral β-dimethylaminoalkylphosphines. Highly efficient ligands for a nickel complex catalyzed asymmetric grignard cross-coupling reaction

Chiral β-dimethylaminoalkylphosphines were prepared starting with amino acids, (S)-alanine, (S)-phenylalanine, (R)-phenylglycine, (S)-valine, and (R)-tert-leucine. The chiral phosphines were found to be highly efficient ligands for a nickel catalyzed asymmetric Grignard cross-coupling reaction (38～94% optical yield).     

Mechanism of the oxidation of cycloheptanone by chloramine-T

The oxidation kinetics of cycloheptanone by chloramine-T in alkaline media has been investigated. A mechanism involving the formation of an intermediate by the interaction between the enolic anion of cycloheptanone and chloramine-T in a slow step followed by its interaction with another molecule of chloramine-T in a fast step leading to products has been proposed. The scheme satisfactorily accords with the observed stoichiometry, negligible influence of ionic strength and a positive dielectric effect. Various rate parameters have been computed and 1.2-cycloheptanedione identified as the end product.With 2 Figures