The general behavior of Newtonian, shear-thinning, shear-thickening, thixotropic, negative thixotropic, and viscoelastic fluids is characterized and briefly discussed in terms of existing theoretical models. Whenever possible, examples of these types of fluids taken from everyday life are given for better understanding. This theoretical introduction is the basis for same, simple, and inexpensive laboratory work employing no special glassware and generally done by pairs of students. The work involves the synthesis of two well-known viscoelastic materials displaying unique properties: poly(vinyl alcohol) (PVA) and white glue, a poly(vinyl acetate)-based emulsion. The students are asked to perform a series of representative mechanical tests on both gels and to describe their observations in full detail. In particular, they are expected to recognize and identify the origin of the intriguing behaviors found (elasticity, spinability, self-siphoning effect, die-swell effect, Weissenberg effect). The tests include the preparation of fibers by extrusion, introducing concepts such as water solubility, hydrogen bonding, and glass transition temperature. The long list of questions, which ideally should be answered at the end of the laboratory work, allows the students to apply the new concepts acquired.

Proton-coupled as well as noise-decoupled '"C NMR spectra of several substituted naphthalenes have been studied. Complete assignments of the ' " C signals based on selectively deuterated derivatives and on the '"C-'H coupling pattern have been made. For the methoxynaphthalenes, acetylnaphthalenes and naphthaldehydes the dominant conformations of the substituents have been deduced from the '"C chemical shifts.

The triterpenoid constituents of the chloroform extract of previously defatted material of the stems of SECURINEGA TINCTORIA were examined and, besides beta-sitosterol beta- D-glucopyranoside, a new oleanolic acid derivative was isolated and identified as 3beta( P-hydroxy- TRANS-cinnamoyloxy)olean-12-en-28-oicacid.

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Proton-coupled and noise-decoupled "C NMR spectra of 1-azulenecnrbaldehyde, 1-acetylazulene and 1,3-azulenedicarbaldehyde have been studied, and complete assignments have been made based on the C-'H coupling constants, additivity of substitoent effects (SIS), and previous assignment for the parent hydrocarbon. The barriers to rotation of the aldehyde group in the above azuleneaubaldehydes and in some naphthaldehydes have been determined by -C dynamic NMR, (DNMR), resulting in free energies of activation of 42.7, 26.8 and 34.4W m0l-l for 1-azulenecarbaldehyde, 1-naphthaldehyde and 2-naphthaldehyde respectively. The same order of barriers is obtained by -012 calculations. A 4-metbxy substitoent in 1-naphthaldehyde and a 6-methoxy substituent in 2-naphthaldehyde increases the rotational barrier by 4.6 and 2.9 W mol-', respectively, whereas a d-methoxy substituent in 2-naphthaldehyde reduces the barrier by 6.7W mol-'. The conformatiom of the dominant rotamers are deduced from -C chemical shifts to be 2 for 1-azuleneuubaldehyde and 1-napbthaldehyde, and E for 2-naphthaldehyde. 13