Identification of genes involved in the regulation of sensory organ precursor formation in Drosophila melanogaster

Defects in early neurogenic development are associated with a wide range of pathological conditions. The Fred protein, a transmembrane IgC2 protein, is necessary for normal development and critical for the Notch signaling pathway. Using Drosophila melanogaster as the model, the regulatory roles of other genes can be studied that exhibit functional interactions with these genes. Macro- and micro-chaeta sensory bristles (large and small bristles) cover the adult fly and provide an avenue to study cell fate. As each bristle originates from an individual sensory organ precursor cell, the presence or absence of sensory bristles indicates sensory organ precursor cell differentiation. From an RNAi mini screen of an array of candidate genes, 2 genes, cullin-2 (cul-2) and tumbleweed (tum), were identified and exhibited a phenotype similar to that of fred, specifically a loss of function. cul-2 is a scaffold protein for ubiquitin ligase, while tum is involved in GTPase inactivation. An additional aim of this study is to understand how these two genes interact within the fred pathway. The two genes were identified using the inducible RNAi / GAL4/ UAS system. The GAL4/UAS system allows one to induce gene specific RNAi in specific tissues and at defined developmental times. Observing the phenotypical consequences of this down regulation occurs at two levels: (1) the adult animal, and (2) in imaginal wing disc of late 3rd instar larvae. Additional studies have been started to further define the phenotype of these genes and their respective interactions with fred gene function. Initial experimental observations suggest that tum, indeed, may have additional roles in the regulation of muscle attachment sites. Furthermore, double mutations of cul-2 and tum, tum and fred, tum and sc are being analyzed to determine potential epistatic relationships.A five-year embargo was granted for this item

Ultrafast switching to a stable hidden topologically protected quantum state in an electronic crystal

Hidden states of matter with novel and unusual properties may be created if a system out of equilibrium can be induced to follow a trajectory to a state which is inaccessible or does not even exist under normal equilibrium conditions. Here we report on the discovery of a hidden (H) topologically protected electronic state in a layered dichalcogenide 1T-TaS2 crystal reached as a result of a quench caused by a single 35 fs laser pulse. The properties of the H state are markedly different from any other state of the system: it exhibits a large drop of electrical resistance, strongly modified single particle and collective mode spectra and a marked change of optical reflectivity. Particularly important and unusual, the H state is stable for an arbitrarily long time until a laser pulse, electrical current or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state. Major observed events can be reproduced by a kinetic model describing the conversion of photo excited electrons and holes into an electronically ordered crystal, thus converting a Mott insulator to a conducting H state. Its long-time stability follows from the topological protection of the number of periods in the electronic crystal.Comment: 21 pages and 5 figures, separate supplementary materia

Controlled vaporization of the superconducting condensate in cuprate superconductors sheds light on the pairing boson

We use ultrashort intense laser pulses to study superconducting state vaporization dynamics in La(2-x)Sr(x)CuO4 (x=0.1 and 0.15) on the femtosecond timescale. We find that the energy density required to vaporize the superconducting state is 2+- 0.8 K/Cu and 2.6 +- 1 K/Cu for x=0.1 and 0.15 respectively. This is significantly greater than the condensation energy density, indicating that the quasiparticles share a large amount of energy with the boson glue bath on this timescale. Considering in detail both spin and lattice energy relaxation pathways which take place on the relevant timescale of picoseconds, we rule out purely spin-mediated pair-breaking in favor of phonon-mediated mechanisms, effectively ruling out spin-mediated pairing in cuprates as a consequence.Comment: 5 pages of article plus 4 pages of supplementary materia

Electron-phonon coupling and charge gap in spin-density-wave iron-pnictides from quasiparticle relaxation dynamics

We investigate the quasiparticle relaxation and low-energy electronic structure in undoped SrFe_2As_2 exhibiting spin-density wave (SDW) ordering using optical pump-probe femtosecond spectroscopy. A remarkable critical slowing down of the quasiparticle relaxation dynamics at the SDW transition temperature T_SDW = 200K is observed. From temperature dependence of the transient reflectivity amplitude we determine the SDW-state charge gap magnitude, 2Delta_SDW/k_BT_SDW=7.2+-1. The second moment of the Eliashberg function, lambda=110+-10meV^2, determined from the relaxation time above T_SDW, is similar to SmFeAsO and BaFe_2As_2 indicating a rather small electron phonon coupling constant unless the electron-phonon spectral function (alpha^2F(omega) is strongly enhanced in the low-energy phonon region

Tracking Cooper Pairs in a Cuprate Superconductor by Ultrafast Angle-Resolved Photoemission

In high-temperature superconductivity, the process that leads to the formation of Cooper pairs, the fundamental charge carriers in any superconductor, remains mysterious. We use a femtosecond laser pump pulse to perturb superconducting Bi2Sr2CaCu2O8+{\delta}, and study subsequent dynamics using time- and angle-resolved photoemission and infrared reflectivity probes. Gap and quasiparticle population dynamics reveal marked dependencies on both excitation density and crystal momentum. Close to the d-wave nodes, the superconducting gap is sensitive to the pump intensity and Cooper pairs recombine slowly. Far from the nodes pumping affects the gap only weakly and recombination processes are faster. These results demonstrate a new window into the dynamical processes that govern quasiparticle recombination and gap formation in cuprates.Comment: 22 pages, 9 figure

Quasiparticle relaxation dynamics in spin-density-wave and superconducting SmFeAsO_{1-x}F_{x} single crystals

We investigate the quasiparticle relaxation and low-energy electronic structure in undoped SmFeAsO and near-optimally doped SmFeAsO_{0.8}F_{0.2} single crystals - exhibiting spin-density wave (SDW) ordering and superconductivity respectively - using pump-probe femtosecond spectroscopy. In the undoped single crystals a single relaxation process is observed, showing a remarkable critical slowing down of the QP relaxation dynamics at the SDW transition temperature T_{SDW}\simeq125{K}. In the superconducting (SC) crystals multiple relaxation processes are present, with distinct SC state quasiparticle recombination dynamics exhibiting a BCS-like T-dependent superconducting gap, and a pseudogap (PG)-like feature with an onset above 180K indicating the existence of a pseudogap of magnitude 2\Delta_{\mathrm{PG}}\simeq120 meV above T_{\mathrm{c}}. From the pump-photon energy dependence we conclude that the SC state and PG relaxation channels are independent, implying the presence of two separate electronic subsystems. We discuss the data in terms of spatial inhomogeneity and multi-band scenarios, finding that the latter is more consistent with the present data.Comment: Replaced by the correct versio

Text, Voice, Image: Staging the Diabolical in Early Modern Italian Musical Theater

In this dissertation, I investigate how belief embeds itself in physical experience and penetrates the rational mind, thereby distorting senses of reality. My analyses focus on the interplay between spectacle, particularly within the sonic domain, and the demonic during the Italian Counter-Reformation. Through an exploration of musical theater and Renaissance demonological treatises, I theorize diabolical stagings in two primary ways. First, I examine demonic nature from a theological perspective, employing Renaissance theories and accounts of the “real” demonic to conceptualize the demon as a theatrical figure—an actor—that engages in the art of temptation. This conceptualization reveals how the demon employs theatrical practice to manifest itself to the spiritual detriment of human actors and audiences. Second, I analyze the theological and political ramifications for audiences and sovereigns—whether secular or clerical—of staging diabolical figures in contexts related to musical theater, including opera libretti, musical intermedi, and full operatic works. I explore how sonic experiences, whether demonically or theatrically produced, contribute to a curated understanding of reality and how these understandings influence human engagement and learning. In each case examined in this dissertation, both real demons and their theatrical counterparts emerge as subversive figures of temptation and control, with profound implications for the actions and worldviews of their audiences. These analyses elucidate the complex dynamics between belief, experience, and perception, demonstrating the potent impact of diabolical stagings on human thought and behavior. I also, therefore, explore the intricate interplay among textual, sonic, and visual representations of the diabolical by scrutinizing depictions of sound-based spectacle through the prism of Renaissance demonological understandings of perception and audition. Generally, theatrical spectacles encompassed a synthesis of visual, auditory, and rhetorical stimuli designed to convey a message to an audience. However, the credibility of visual representation becomes particularly low within the realm of demonic theater. In both offstage demonic phenomena perceived by spectators and in theatrical spectacles, visual effects can be readily manipulated to evoke specific emotional responses in viewers. The work of Nicola Sabbatini (1574-1653), especially his Pratica di fabricar scene, e machine ne’ teatri (1638), exemplifies the extent to which theaters sought to influence audiences’ emotional reactions through elaborate stage machinery and scenic design. I argue that the objects of my study made apparent the tensions between visual stimuli and the immaterial phenomena of emotional reactions and intellectual and spiritual senses of reality. In doing so, they heightened the stakes for audiences who believed that real demons could access the capacity of visual stimuli to grab the attention of viewers. This would open an avenue to interact with and manipulate the viewers’ understanding of what they see and subsequently with how they conceptualize their world depending on the performer’s desires, be they political, theological, or otherwise.</p