Dynamical Casimir effect and the structure of vacuum in quantum field theory

Some of the most interesting phenomena that arise from the developments of the modern physics are surely vacuum fluctuations. They appear in different branches of physics, such as Quantum Field Theory, Cosmology, Condensed Matter Physics, Atomic and Molecular Physics, and also in Mathematical Physics. One of the most important of these vacuum fluctuations, sometimes called "zero-point energy", as well as one of the easiest quantum effect to detect, is the so-called Casimir effect. The purposes of this thesis are: - To propose a simple retarded approach for dynamical Casimir effect, thus a description of this vacuum effect when we have moving boundaries. - To describe the behaviour of the force acting on a boundary, due to its self-interaction with the vacuum.

A novel allele of FILAMENTOUS FLOWER reveals new insights on the link between inflorescence and floral meristem organization and flower morphogenesis

Background The Arabidopsis FILAMENTOUS FLOWER (FIL) gene encodes a YABBY (YAB) family putative transcription factor that has been implicated in specifying abaxial cell identities and thus regulating organ polarity of lateral organs. In contrast to double mutants of fil and other YAB genes, fil single mutants display mainly floral and inflorescence morphological defects that do not reflect merely a loss of abaxial identity. Recently, FIL and other YABs have been shown to regulate meristem organization in a non-cell-autonomous manner. In a screen for new mutations affecting floral organ morphology and development, we have identified a novel allele of FIL, fil-9 and characterized its floral and meristem phenotypes. Results The fil-9 mutation results in highly variable disruptions in floral organ numbers and size, partial homeotic transformations, and in defective inflorescence organization. Examination of meristems indicates that both fil-9 inflorescence and floral meristems are enlarged as a result of an increase in cell number, and deformed. Furthermore, primordia emergence from these meristems is disrupted such that several primordia arise simultaneously instead of sequentially. Many of the organs produced by the inflorescence meristems are filamentous, yet they are not considered by the plant as flowers. The severity of both floral organs and meristem phenotypes is increased acropetally and in higher growth temperature. Conclusions Detailed analysis following the development of fil-9 inflorescence and flowers throughout flower development enabled the drawing of a causal link between multiple traits of fil-9 phenotypes. The study reinforces the suggested role of FIL in meristem organization. The loss of spatial and temporal organization of fil-9 inflorescence and floral meristems presumably leads to disrupted cell allocation to developing floral organs and to a blurring of organ whorl boundaries. This disruption is reflected in morphological and organ identity aberrations of fil-9 floral organs and in the production of filamentous organs that are not perceived as flowers. Here, we show the role of FIL in reproductive meristem development and emphasize the potential of using fil mutants to study mersitem organization and the related effects on flower morphogenesis.

Musical Expertise and Melodic Structure in Memory for Musical Notation

Two experiments plus a pilot investigated the role of melodic structure on short-term memory for musical notation by musicians and nonmusicians. In the pilot experiment, visually similar melodies that had been rated as either "good" or "bad" were presented briefly, followed by a 15-sec retention interval and then recall. Musicians remembered good melodies better than they remembered bad ones: nonmusicians did not distinguish between them. In the second experiment, good, bad, and random melodies were briefly presented, followed by immediate recall. The advantage of musicians over nonmusicians decreased as the melody type progressed from good to bad to random. In the third experiment, musicians and nonmusicians divided the stimulus melodies into groups. For each melody, the consistency of grouping was correlated with memory performance in the first two experiments. Evidence was found for use of musical groupings by musicians and for use of a simple visual strategy by nonmusicians. The nature of these musical groupings and how they may be learned are considered. The relation of this work to other studies of comprehension of symbolic diagrams is also discussed.

A New Crystalline LiPON Electrolyte: Synthesis, Properties, and Electronic Structure

The new crystalline compound, Li2PO2N, was synthesized using high temperature solid state methods starting with a stoichiometric mixture of Li2O, P2O5, and P3N5. Its crystal structure was determined ab initio from powder X-ray diffraction. The compound crystallizes in the orthorhombic space group Cmc2(1) (# 36) with lattice constants a = 9.0692(4) angstrom, b = 53999(2) angstrom, and c = 4.6856(2) angstrom. The crystal structure of SD-Li2PO2N consists of parallel arrangements of anionic chains formed of corner sharing (PO2N2) tetrahedra. The chains are held together by Li+ cations. The structure of the synthesized material is similar to that predicted by Du and Holzwarth on the basis of first principles calculations (Phys. Rev. B 81,184106 (2010)). The compound is chemically and structurally stable in air up to 600 degrees C and in vacuum up to 1050 degrees C. The Arrhenius activation energy of SD-Li2PO2N in pressed pellet form was determined from electrochemical impedance spectroscopy measurements to be 0.6 eV, comparable to that of the glassy electrolyte LiPON developed at Oak Ridge National Laboratory. The minimum activation energies for Li ion vacancy and interstitial migrations are computed to be 0.4 eV and 0.8 eV, respectively. First principles calculations estimate the band gap of SD-Li2PO2N to be larger than 6 eV. (C) 2013 Elsevier B.V. All rights reserved.