Structure of the molten salt methyl ammonium nitrate explored by experiments and theory.

We present an analysis of the structure of the monomethylammonium nitrate (MMAN) compound. Vibrational Raman spectroscopy and X-ray powder diffraction have been used to characterize the bulk phases of MMAN, and assignment of the resonant frequencies has been performed by ab initio (DFT) computations on small clusters of the compound. The theoretical spectra are in excellent agreement with the experimental ones and provide a means by which an interpretation of the hydrogen-bonding network that exists in such compound can be analyzed. In particular, we found that the spectrum of one of the solid phases is structurally very similar to that of the liquid. We present experimental evidence for the existence of such phase both from X-ray data and Raman spectra which, in turn, is easily interpreted with a one-to-one correspondence with the ab initio simulation of the small clusters. A geometric structure of the short-range local arrangement in these two bulk phases is therefore proposed.

Normal modes of a quasi-one-dimensional multichain complex plasma.

We studied equally charged particles, suspended in a complex plasma, which move in a plane and interact with a screened Coulomb potential (Yukawa type) and with an additional external confining parabolic potential in one direction, which makes the system quasi-one-dimensional (Q1D). The normal modes of the system are studied in the presence of dissipation. We also investigated how a perpendicular magnetic field couples the phonon modes with each other. Two different ways of exciting the normal modes are discussed: (1) a uniform excitation of the Q1D lattice, and (2) a local forced excitation of the system in which one particle is driven by, e.g., a laser. Our results are in very good agreement with recent experimental findings on a finite single chain system [Phys. Rev. Lett. 91, 255003 (2003)]]. Predictions are made for the normal modes of multichain structures in the presence of damping.

Aggression.

Pathologic aggression can be evaluated in terms of its psychosocial provocations, but it also must be recognized as a physiologically generated behavior and that disruptions of those controlling physiologic mechanisms can lead to pathologic states of aggression. Laboratory and clinical evidence indicates that the phylogenetically older limbic system is the anatomic core and that serotonin is the major neurotransmitter linked to that behavior. Hormonal factors influence aggression but are, to a large extent, altered by the aggressive acts themselves. There are a number of recognizable clinical syndromes which, by producing abnormal activity in limbic structures, by interfering with higher cortical control, or by causing neuroendocrine dysfunction, lead to states of pathologic aggression.