866 research outputs found
Orbital Contributions to the Electron g Factor in Semiconductor Nanowires
No full textRecent experiments on Majorana fermions in semiconductor nanowires [S. M. Albrecht, A. P. Higginbotham, M. Madsen, F. Kuemmeth, T. S. Jespersen, J. Nygård, P. Krogstrup, and C. M. Marcus, Nature (London) 531, 206 (2016)NATUAS0028-083610.1038/nature17162] revealed a surprisingly large electronic Landé g factor, several times larger than the bulk value - contrary to the expectation that confinement reduces the g factor. Here we assess the role of orbital contributions to the electron g factor in nanowires and quantum dots. We show that an L·S coupling in higher subbands leads to an enhancement of the g factor of an order of magnitude or more for small effective mass semiconductors. We validate our theoretical finding with simulations of InAs and InSb, showing that the effect persists even if cylindrical symmetry is broken. A huge anisotropy of the enhanced g factors under magnetic field rotation allows for a straightforward experimental test of this theory.</p
Mearuring the orientation and roation rate of 3D printed particles in turbulence
No full textThe orientation distribution and rotations of anisotropic particles in turbulent flows play a key role in many applications ranging from icy clouds to papermaking and drag reduction in pipe flow. However, experimental access to time-resolved orientations of anisotropic particles has not been easy to achieve. The use of 3D printing opens up the possibility to fabricate a wide range of particle shapes with smallest dimension down to 300 μm. So far, we have printed rods, crosses, jacks, triads, tetrads and helical particle shapes. We extract particle orientations from stereoscopic video images using a method of least squares optimization in Euler angle space. We find that in turbulence, the orientation and rotation-rate of many particles can be understood using a simple picture of alignment of both the vorticity and a long axis of the particle with the Lagrangian stretching direction of the flow
Modelling meristem development in plants
No full textMeristems continually supply new cells for post-embryonic plant development and coordinate the initiation of new organs, such as leaves and flowers. Meristem function is regulated by a large and interconnected dynamic system that includes transcription networks, intercellular protein signalling, polarized transport of hormones and a constantly changing cellular topology. Mathematical modelling, in which the dynamics of a system are simulated using explicitly defined interactions, can serve as a powerful tool for examining the expected behaviour of such a system given our present knowledge and assumptions. Modelling can also help to investigate new hypotheses in silico both to validate ideas and to obtain inspiration for new experiments. Several recent studies have used new molecular data together with modelling and computational techniques to investigate meristem function
Auxin is not asymmetrically distributed in initiating Arabidopsis leaves
No full textAbstractIt has been proposed that asymmetric auxin levels within initiating leaves help establish leaf polarity, based in part on observations of the DII auxin sensor. Here we show that the mDII control sensor also exhibits an asymmetry and that according to the ratio-metric auxin sensor R2D2, no obvious asymmetry in auxin exists. Together with other recent findings, our results argue against the importance of auxin asymmetry in establishing leaf polarity.</jats:p
Portfolio of recorded performances and exegesis: Messiaen’s musical language for the jazz pianist - an exploration through performance.
No full textMoving beyond Gunther Schuller’s Third Stream amalgamation of classical and jazz, this study explores whether the musical language of Olivier Messiaen can make a valid contribution to jazz piano performance. Initially, my project sought to answer such questions as: What elements of the musical language of Messiaen already exist in the jazz vocabulary? Am I able to extend this further? What are the timbral structures and pianistic effects within Messiaen’s musical language? What will be the most effective application of Messiaen’s musical language to jazz piano performance? Endeavouring to answer the final question led me to consider such aspects as whether the project should be limited to quoting Messiaen motifs, arranging Messiaen melodies, replacing jazz harmonic structures on standards with examples from Messiaen’s musical language or whether it would be better to approach the research conceptually. The work of Hubert Nuss provided encouraging reassurance that this was not an impossible task. In order to articulate this conception, the initial challenge was to decide how the classical and jazz worlds might meet in a ‘Messiaen’ technique. The approach adopted was similar to that used for undergraduate jazz study, namely, immersion in the piano scores and recordings of Messiaen’s music as well as by live performances. This was followed by the development and assessment of a contrived approach when specific techniques, such as tonal colourings or harmonic structures, were developed through prepared exercises and consciously included in my performance. It was then compared with an intuitive approach when no such precise parameters were established. This submission consists of CD recordings of two public recitals and an exegesis. It documents the development of this Messiaen technique and discusses its application in my performances. It also demonstrates the ways that Messiaen’s musical language can be used within jazz piano performance to provide a colour that distinguishes jazz piano performance in a competitive field.Thesis (M.Mus.) -- University of Adelaide, Elder Conservatorium of Music, 201
Self-organizing periodicity in development: organ positioning in plants
No full textABSTRACTPeriodic patterns during development often occur spontaneously through a process of self-organization. While reaction-diffusion mechanisms are often invoked, other types of mechanisms that involve cell-cell interactions and mechanical buckling have also been identified. Phyllotaxis, or the positioning of plant organs, has emerged as an excellent model system to study the self-organization of periodic patterns. At the macro scale, the regular spacing of organs on the growing plant shoot gives rise to the typical spiral and whorled arrangements of plant organs found in nature. In turn, this spacing relies on complex patterns of cell polarity that involve feedback between a signaling molecule – the plant hormone auxin – and its polar, cell-to-cell transport. Here, we review recent progress in understanding phyllotaxis and plant cell polarity and highlight the development of new tools that can help address the remaining gaps in our understanding.</jats:p
Notocomplana palta (Marcus 1954) Faubel 1983
No full textNotocomplana palta (Marcus 1954) Faubel 1983 Synonym: Notoplana palta Marcus 1954 Material examined. Specimens of Notocomplana palta were provided by the Swedish Museum of Natural History, Stockholm, Sweden (SMNH). We designate as lectotype the specimen SMNH 110097- 110101 from the series of animals studied by Marcus (1954). New specimens were collected in 2006–2009 at different localities along the Patagonian coast; these are housed in the Invertebrate Zoology collection at the MLP (Table 1, Figure 1). Description. Live specimens are light to dark orange-colored (Figure 5 B). Central zone where pharynx is placed is darker. Body ovate and with ruffled edges. Studied specimens measure 10–20 mm long and 5–9 mm wide. Tentacles absent. Eyes placed in medial region, associated to brain zone. Brain eyes rounded, small, numbering 35 to 40 on each side. Tentacular eyes posterior to brain eyes, larger, and approximately ten on each side. Very small eyes in parenchyma ventrally and anteriorly to brain (Figure 5 A). Ventral and dorsal epidermis ciliated. Ventral cilia longer. Rhabdites on both surfaces, more abundant on ventral epidermis. Basal membrane thick, the ventral one being thinner than the height of the epithelium; dorsal basal membrane thickness equal to the epithelium height, folded in some of the thin sections. Body-wall musculature on dorsal surface consisting of an external thin circular layer, a diagonal middle layer (the thickest) and a longitudinal internal layer; a second internal circular layer is crossed by dorso-ventral muscles. On the ventral surface of the body, musculature is longitudinal, followed internally by a thin circular layer; the latter is packed inwards. Pharynx ruffled (approximately nine folds), placed in front of mid-length of body. Epithelium lining the pharynx cavity is ciliated. Mouth slightly behind mid-length of pharynx (Figure 5 C). Testicles ventral and ovaries dorsal, distributed throughout body length, including the region in front of the brain. Deferent ducts (one pair) thickenning and twisting before joining seminal vesicle. Seminal vesicle strongly muscular, rounded to oval. Ejaculatory duct long, thin and muscular. A short portion of ejaculatory duct projects into prostatic vesicle, which shows a tall and folded epithelium. Lumen of prostatic vesicle continuous with the lumen of penis papilla (Figure 4). Penis papilla conical, located in a male atrium and opening into a male pore (Figure 5 E, H–I). Female gonopore posterior to male pore (Figure 4). Muscular vagina inlaid with ciliate epithelium; shape sigmoidal, and lying perpendicular to surface in its first part, then running anteriorly, and later turning posteriorly. In female specimens, the portion reaching anteriorly carries abundant cement glands that open into that part of the vagina (Figures 4, 5 D, F). Uteri loaded with ovocites and continuing into two uterine ducts that join to form a single ciliate duct. The latter joins the proximal part of vagina at its ventral surface. Lang´s vesicle channel present after junction of uterus and vagina. This channel shows constrictions that give it a beaded appearance; it opens into Lang’s vesicle. At the junction of vesicle and duct there is a sphincter. Vesicle rounded to ovate, lined with a tall vacuolar epithelium, with scarce muscular fibres. Sperms were observed within it (Figures 4, 5 D, G). Remarks. This species was originally described by Marcus (1954) from the fjord region in southern Chile. The Patagonian specimens clearly agree with the original description of the species (Marcus, 1954) and with the material he had available for study (SMNH 110097- 110101). Bulnes (2009) recently mentioned Notocomplana palta in an area close to the type locality but the description given by this author does not agree with the original desciption (Marcus, 1954). Bulnes (2009) described small tentacles, a thin and short penis papilla, and a four-chambered seminal vesicle. These structures were not mentioned in the original description of this species (Marcus, 1954) nor are they present in the material studied by him and housed in the SMNH. Therefore, they can not be considered part of this taxon. The material housed in the SMNH was not designated originally as type material. To avoid future misidentifications of Notocomplana palta, the specimen described and illustrated by Marcus in the original work (Marcus 1954; 65; figs. 99, 101) and from the type locality (as recorded on the original label St. M 21) is designated as the lectotype under Article 74 of the fourth edition of ICZN (1999). The presence of this species along the Patagonian coast and southern Chile suggests a Magellanic distribution similar to that of other species of invertebrates (e.g. Boschi 2000, Balech & Ehrlich 2008).Published as part of Brusa, Francisco & Damborenea, Cristina, 2011, Polycladida Acotylea from Patagonia. Redescription of Crassiplana albatrossi (Pseudostylochidae), lectotype designation and first record of Notocomplana palta (Notoplanidae), pp. 29-38 in Zootaxa 2903 on pages 34-36, DOI: 10.5281/zenodo.20113
FOUR-POINT CORRELATIONS OF MOLECULAR FLUCTUATIONS BY TWO-DIMENSIONAL OPTICAL SPECTROSCOPY
No full textP. F. Tekavec, G. A. Lott, and A. H. Marcus, J. Chem. Phys. 127, 214307 (2007).Author Institution: Department of Physics and Oregon Center for Optics; Department of Chemistry and Oregon Center for Optics, Eugene, OR 97403Two-dimensional phase modulation electronic coherence spectroscopy (PM-ECS) is a phase-selective fluorescence detection technique that is uniquely suited to study the interplay between coherent and incoherent coupling between optical transitions of molecular complexes }. The fluorescence detection aspect of this method is advantageous to study the electronic energy transfer between chromophores of the tetrameric fluorescent protein DsRed in the visible regime. DsRed is a model energy transfer complex to study strong coupling effects between chromophores in an otherwise dilute sample and also to study the effects of both vibrational and thermal decoherence. Novel aspects of this technique and current progress will be presented
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