The possibility of different time scales in the dynamics of pore imbibition

To model the imbibition of liquids into porous solids, use is often made of the Lucas-Washburn equation, which relates the distance of penetration of a liquid at a given time to the pore radius, the viscosity and surface tension of the liquid, and the effective contact angle between the liquid and the solid. In this paper, we extend previous large-scale molecular dynamics simulations to show how this tool can be used to study the details of liquid imbibition, including the impact of the contact angle on the dynamics of penetration and the evolution of the internal flow field. In particular, we show that the asymptotic behavior of the contact angle versus time for a completely wetting liquid is given by approximately t(-1/4).     

Effect of Hydration–Dehydration Processes on the Structure and Porosity of Detemplated Silica Fibers

A study was carried out on the conditions of template removal (calcination or extraction by solvents) and hydration–dehydration processes on the hexagonal structure and porosity of detemplated fibers. The hydration–dehydration cycle leads to a decrease in fiber porosity, especially in fiber detemplation by extraction with surfactant solvents such as ethanol and acetic acid.     

Thio-claisen rearrangements of some ketene derivatives

A number of 1-allylthio and 1-crotylthio 1-aminoalkenes derived from ketones and active methylene compounds has been prepared and rearranged to the corresponding thioamides (thio-Claisen rearrangement). Besides rearrangement products, small amounts of 1-alkyl-thio-N-alkyl-N-phenyl-1-aminoalkenes have also been isolated. When the ketene derivatives did possess a H-atom on nitrogen, cleavage of the formed thioamide produced phenyl isothiocyanate and substituted active methylene compounds.     

Dielektrische Relaxation Polymerer bei Temperaturen bis 1 °K

Zusammenfassung Es werden Messungen des dielektrischen Verlustes tan im Temperaturbereich von 1 bis 80 °K und bei verschiedenen Frequenzen zwischen 10 Hz und 10 kHz an einer Reihe von Polymeren mitgeteilt.Der dielektrische Verlust sinkt im allgemeinen mit Annäherung an den absoluten Nullpunkt monoton ab. Es scheint dies anzudeuten, daß immer ein dielektrischer Untergrund, beruhend auf allgemeinen thermischen Fluktuationen, existiert, der im übrigen für Polymere mit polaren Gruppen höher liegt als für unpolar gebaute. Zu tiefsten Temperaturen hin überlagert sich diesem allgemeinen Trend oft noch ein Maximum, wenngleich bei Temperaturen bis 1 °K herab zuweilen nur erst in einer Konstanz der Verlustwinkel-Werte angedeutet. Es sieht also so aus, als ob auch noch bei tiefsten Temperaturen singuläre Relaxationsmechanismen eine Rolle spielen können. In einer Reihe von Fällen findet man weitere Relaxationsprozesse zwischen 15 und 40 °K.Soweit sich Aktivierungsgrößen aus der Auftragung der Maximallage in der Temperatur mit der Frequenz nach Abtrennung des allgemeinen Untergrundes abschätzen lassen, werden diese mit sinkender Temperaturlage immer kleiner.Die dielektrischen Verluste sind in allen Fällenextrem abhängig von der Vorgeschichte der Proben und zwar insofern, daß offensichtlich Verspannungen im Material infolge von Deformationsprozessen und anderen Behandlungen zu einer erheblichen Erhöhung der Verluste führen, sowohl des Untergrundes als der singulären Mechanismen.

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Summary Investigations of dielectric loss in the temperature range 1–80 °K and with frequencies between 10 c/sec and 10 kc/sec for diverse polymers a presented. For all polymers the dielectric loss decreases in principle monotonely with the approximation of the absolute Zero-point.Thus we suppose the existence of a common dielectric background loss depending from the thermal fluctuations in the material. Moreover this background losses are higher for substances with polar groups.At the lowest temperatures in most cases there seems to appear a loss peak. For temperatures down to 1 °K often this can be only suggested from the constancy of losses. But it seems to be a quite normal fact, that for extremely deep temperatures something as a singular relaxation mechanism may exist.Further discrete mechanisms exist for the range between 15 and 40 °K. Activation energy evaluated formally from the experimental dates in the normal manner after separation of the peaks from the background becomes smaller and smaller with decreasing temperatures.In all investigated cases the dielectric losses are very sensible to prehistory of the samples. It seems, that expecially stress, by deformation and other treatments, gives rise for an increase of loss for the background as for discrete mechanisms.

     

Pyrimidines

The reaction of cyclohexanone with arylidenebisureas (e.g. benzal-bisurea) in an acid medium has given 4, 4-diaryl-2, 2-dioxo-5, 5-trimethylene-6, 6-spirobishexahydropyrimidines (II). The acid hydrolysis of IIa (aryl-C₆H₅) in the presence of 2, 4-dinitrophenylhydrazine leads to the 2, 4-dinitrophenylhydrazone of 2-hydroxy-8-oxo-4-phenyl-5, 6, 7, 8-tetrahydroquinazoline (IV). Compound IV was also obtained by the ozonization of 2-acetoxy-8-benzal-4-phenyl-5, 6, 7, 8-tetrahydroquinazoline (IX) and subsequent decomposition of the ozonide with a solution of 2, 4-dinitrophenylhydrazine. The structure of the compounds obtained was confirmed by means of their IR, UV, and PMR spectra. Corresponding 6, 6-spirobishexahydropyrimidines have also been obtained from 2-methylcyclohexanone, acetone, and methyl ethyl ketone and benzalbisurea.For part XIV, see [1].     

Structure of polymers obtained from sulfur monochloride and olefins containing sulfonium salt structures

Reactions of sulfur monochloride with diolefins lead to polymeric products which can be reduced to diepisulfides in low yield. In reactions with cyclic triolefins, polymers containing tricyclic sulfonium structures are obtained as a results of transannular additions and subsequent transannular displacements. Due to the insolubility and reactivity of these ionic structures, only incomplete structural assignements could be made, but the reactions are studied on similar cyclic structures which provide model systems.     

The vinylation of benzotriazole

The reaction of benzotriazole with acetylene under pressure in the presence of potassium hydroxide and cuprous chloride has been examined. 1-Vinylbenzotriazole was obtained in 75% yield.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1289–1290, September, 1970.     

Structure of convosine

From the roots of the plantConvolvulus subhirsutum Regel et Schmalh. have been isolated seven known alkaloids and one new one, for which, on the basis of spectral characteristics, a comparative study with known alkaloids of the tropane series, and synthesis, the structure of (+)-N-isopropyl-3-veratroyloxynortropane has been established.Institute of the Chemistry of Plant Substances of the Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 618–620, September–October, 1986.     

Über Spurenelementbestimmungen in Leberproben Mittels Protoneninduzierter Röntgenfluoreszenz (Pixe)

Multi-element-analysis by PIXE in respect to medical applications is discussed. Examples of trace-element determinations in liver tissues are given, demonstrating the applicability and usefulness of this rather new analytical technique.      

Oxydation photochimique d'amines tertiaires et d'alcaloideS—IX: Oxydation photochimique d'alcaloides quinolizidiniques et indolizidiniques tetracycliques: sparteine et α-isosparteine,lupanine et α-isolupanine,camoensidine et tetrahydroleontidine

The influence of ring size and ring conformation on the site of photosensitized oxidation of tertiary amines was illustrated by the photooxidation of tetracyclic indolizidine and quinolizidine alkaloids. An amino radical intermediate has been supposed during photooxidation of lupanine sensitized by eosin under nitrogen atmosphere.