Die N-(4'-Nitrophenacyl)-arylamine 5 , hergestellt aus den Arylaminen 3 und 4-Nitrophenacylbromid (2), haben in Abhangigkeit von den Arylsubstituenten eine gelbe, rote oder violette Farbe. Sie wird zuriickgefiihrt auf intramolekulare Wechselwirkung zwixhen dem Nitrobenzoylsystem als Elektronenacceptor und dem Arylaminteil als Elektronendonator. Bei Acetylierung des Aminstickstoffs geht die Farbe verloren. Fur ein Gleichgewicht zwischen den Aminen 5 und den N-(4'-Nitrostyryl)-arylaminen 7 gibt es keine Hinweise.

No abstract

LETTERS TO THE EDITORAs is usual in this type of calculation 6 we suppose these differences of the localization energies to be equal to the differences of the activation energies. As the activation entropies are constant to a good approximation,6 we may calculate the percentage of meta isomer in the reaction product from the values of e. and a.k, which in turn are obtained from the data on bond distances and dipole moments from the literature. Some of the results of our calculations are shown in Table 1.The agreement between our results and the experimental values is surprisingly good for the first group of substituents. For the second group all theoretical values are higher than the experimental results, which is ascribed to the hyperconjugation of the -CH3 and -CH2X group with the pentadienate cation, which tends to lower the energy of the transition state for ortho and para substitution. This effect of hyperconjugation was not taken into account in the present calculations. 1 M. J. S. Dewar, The Electronic Theory of Organic Chemistry (The Clarendon Press, Oxford, 1949). 2 We use the same convention of sign as Dewar (I.e.) '

Most common forms of haptic feedback use vibration, which immediately captures the user's attention, yet is limited in the range of strengths it can achieve. Vibration feedback over extended periods also tends to be annoying. We present compression feedback, a form of haptic feedback that scales from very subtle to very strong and is able to provide sustained stimuli and pressure patterns. The demonstration may serve as an inspiration for further work in this area, applying compression feedback to generate subtle, intimate, as well as intense feedback.

Nachdem jahrzehntelang die yon I~ONA angegebene stalagmometrische Bestimmung der Serumlipase allein gebr~iuch]ich war, wurde in