<Emphasis Type="Italic">N</Emphasis>-Methyl-D-aspartic Acid (NMDA) in the nervous system of the amphioxus <Emphasis Type="Italic">Branchiostoma lanceolatum</Emphasis>

Background  

NMDA (N-methyl-D-aspartic acid) is a widely known agonist for a class of glutamate receptors, the NMDA type. Synthetic NMDA elicits very strong activity for the induction of hypothalamic factors and hypophyseal hormones in mammals. Moreover, endogenous NMDA has been found in rat, where it has a role in the induction of GnRH (Gonadotropin Releasing Hormone) in the hypothalamus, and of LH (Luteinizing Hormone) and PRL (Prolactin) in the pituitary gland.     

A Minimax Theorem in Banach Lattices

This paper is mainly concerned with measures which take their values in a Banach lattice. Examples of capacities are given and a type of minimax theorem for vector capacities is proved.     

Prevalence and structure of adding machines for cellular automata

Consider the collection of left permutive cellular automata Φ with no memory, defined on the space S of all doubly infinite sequences from a finite alphabet. There exists , a dense subset of S, such that is topologically conjugate to an odometer for all so long as Φm is not the identity map for any m. Moreover, Φ generates the same odometer for all . The set is a dense Gδ subset with full measure of a particular subspace of S.     

Influence of water on the physical aging of poly(ethylene terephtalate)

Physical aging in polyethylene terephtalate (PET) has been studied on samples well characterized in terms of aging history and their content of water. This allows us to better understand the role played by water in the complex phenomenology of the physical aging in a hygroscopic material as PET. No appreciable changes in the thermal behavior in the sample aged in water at room temperature for one month were noted, while substantial changes were observed in samples aged in more severe conditions like 50°C under vacuum and 50°C in water for one month. The results are consistent with the formation of small regions in which segments of chains are closely packed.     

Recognition of the syndiotactic polypropylene polymorphs via dynamic-mechanical analysis

Three syndiotactic polypropylene samples were crystallized under different conditions in order to obtain different polymorphs. A first sample was crystallized at high temperature, obtaining the helical form I; a second was crystallized from the melt at 0°C for many days obtaining the trans-planar mesophase; a third sample was obtained by solvent induced crystallization followed by annaeling of the trans-planar mesophase, leading to a mixture of both the helical forms I and II. In the dynamic-mechanical analysis the helical form I showed only one peak of tan δ corresponding to the amorphous glass transition. The other polymorphs also showed this transition centered at about the same temperature. Beside the peak corresponding to the Tg, the trans-planar mesophase was characterized by a peak appearing at 70°C, and the helical form II by a peak at 100°C. These peaks, unambiguously associated to transitions of the different forms, can be considered a distinctive evidence for the polymorphs obtained in different processing conditions.     

Cast-extruded syndiotactic polypropylene films: preliminary structural and mechanical results

Syndiotactic polypropylene (sPP) was cast-extruded with a laboratory single screw extruder, obtaining a crystalline and still highly transparent film. The structural studies showed that the film crystallized at room temperature in the disordered helical form I, containing a fraction of a mesophase with the chains in trans-planar conformation. X-ray patterns, taken either along the extrusion direction (MD) or along the orthogonal directions (TD and ND), indicated a low orientation of the c axis parallel to the machine direction (MD) and a partial orientation of the a axis along the transverse direction (TD). Mechanical properties performed in either direction showed a very similar behaviour, but a different strain at the breaking point. The mechanical parameters were derived in both directions.     

Elastic Behaviour of Oriented Syndiotactic Poly(propylene)

A syndiotactic poly(propylene) film (sPP), quenched from the melt at 0°C, was drawn at room temperature up to a draw ratio of λ = 6. The fibre was analysed under tension by X‐ray analysis and FTIR spectroscopy, showing the presence of the oriented crystalline form III described by Chatani, with the chains in trans‐planar conformation. Then it was unhooked, undergoing a large shrinkage, and reaching a length corresponding to a draw ratio of λ = 3.8. X‐ray and FTIR analysis showed that in the relaxed fibre, a conformational transition from the trans‐planar to the helical form occurred. The relaxed fibre was again submitted to increasing extensions up to λ = 6, step by step, and the elastic behaviour was analysed through the Mullins' curve and hysteresis cycles. It showed good elastic properties, which appear to be closely correlated to the conformational transition between helical and trans‐planar forms.     

Ubiquity of odometers in topological dynamical systems

Let M be the Cantor space or an n-manifold with C(M,M) the set of continuous self-maps of M. We prove the following:

(1)

There is a residual set of points (x,f) in M×C(M,M) all of which generate as their ω-limit set a particular, unique adding machine.

(2)

Moreover, if M has the fixed point property, then a generic f∈C(M,M) generates uncountably many distinct copies of every possible adding machine.