On the nematic-nematic phase transition in mixtures composed of sheet-shaped palladium organyls and apolar organic solvents

The three sheet-shaped palladium organyls 1a-c exhibit lyotropic nematic properties in apolar organic solvents. The occurrence of two nematic lyomesophases was verified by the investigation of the orientational properties of these liquid crystalline systems. In cells with obliquely deposited SiO_x layers, the director of the high temperature phase N₂ is aligned in a homogeneous, planar manner. In the low temperature phase N₁, a different orientational pattern is observed. The specific pattern type depends on the deposition conditions of the SiO_x layers. In samples homeotropically aligned in the N₂ phase, the director is tilted away from the cell normal after the transition into the N₁ phase. These changes of orientation are reversible. The experimental observations presented here support our proposed model for the structural change at the nematic-nematic phase transition.     

On the magnetic structure of low Ni-I boracite

Possible spin arrangements of the ferromagnetoelectric Ni-I boracite are discussed from a microphysical point of view. Rotation of the spontaneous magnetization by 90° with reversal of the spontaneous polarization is explained.     

The earliest reckoning books existing in the Persian language

Two reckoning books edited recently in Teheran help to form an image of the hitherto almost unknown astronomer and mathematician Ab$\text{u}$ Ja'far Muh. b. Ayy$\text{u}$b $\text{T}\text{?}$abar$\text{i}$ who lived in $\text{A}$mul near the Caspian during the Saljuq period and observed from 1068 to 1092 A.D. The first of the said books is a textbook of Hindi reckoning similar to al-Nasaw$\text{i}$'s reckoning book (1029); the second one teaches mental calculation and application of both methods to everyday problems, much in the line of Ab$\text{u}$ al-Waf$\text{a}$'s reckoning book (c. 980 A.D.). Both texts are on a rather elementary level and include some errors, but they reveal their author as a skilled teacher and expound some interesting problems not found elsewhere. Moreover, they deserve our attention as the most ancient existing arithmetic treatises in the Persian language known so far.     

Über Defektbegriffe in der Theorie der meromorphen Funktionen

Ohne Zusammenfassung     

Fluoreszenz von 4,4′-disubstituierten 1,3-Diphenyl-2pyrazolinen mit Donator-Akzeptor-Substituen

Ohne Zusammenfassung