CO ro-vibrational lines in HD100546: A search for disc asymmetries and the role of fluorescence

We have studied the emission of CO ro-vibrational lines in the disc around the Herbig Be star HD100546 with the final goal of using these lines as a diagnostic to understand inner disc structure in the context of planet formation. High-resolution IR spectra of CO ro-vibrational emission at eight different position angles were taken with CRIRES at the VLT. From these spectra flux tables, CO ro-vibrational line profiles, and population diagrams were produced. We have investigated variations in the line profile shapes and line strengths as a function of slit position angle. We used the thermochemical disc modelling code ProDiMo based on the chemistry, radiation field, and temperature structure of a previously published model for HD100546. Comparing observations and the model, we investigated the possibility of disc asymmetries, the excitation mechanism (UV fluorescence), the geometry, and physical conditions of the inner disc. The observed CO ro-vibrational lines are largely emitted from the inner rim of the outer disc at 10-13 AU. The line shapes are similar for all v levels and line fluxes from all vibrational levels vary only within one order of magnitude. All line profile asymmetries and variations can be explained with a symmetric disc model to which a slit correction and pointing offset is applied. Because the angular size of the CO emitting region (10-13 AU) and the slit width are comparable the line profiles are very sensitive to the placing of the slit. The model reproduces the line shapes and the fluxes of the v=1-0 lines as well as the spatial extent of the CO ro-vibrational emission. It does not reproduce the observed band ratios of 0.5-0.2 with higher vibrational bands. We find that lower gas volume densities at the surface of the inner rim of the outer disc can make the fluorescence pumping more effcient and reproduce the observed band ratios.Comment: 20 pages, 21 figure

TEXES Observations of M Supergiants: Dynamics and Thermodynamics of Wind Acceleration

We have detected [Fe II] 17.94 um and 24.52 um emission from a sample of M supergiants using TEXES on the IRTF. These low opacity emission lines are resolved at R = 50, 000 and provide new diagnostics of the dynamics and thermodynamics of the stellar wind acceleration zone. The [Fe II] lines, from the first excited term, are sensitive to the warm plasma where energy is deposited into the extended atmosphere to form the chromosphere and wind outflow. These diagnostics complement previous KAO and ISO observations which were sensitive to the cooler and more extended circumstellar envelopes. The turbulent velocities, Vturb is about 12 to 13 km/s, observed in the [Fe II] forbidden lines are found to be a common property of our sample, and are less than that derived from the hotter chromospheric C II] 2325 Angstrom lines observed in alpha Ori, where Vturb is about 17 to 19 km/s. For the first time, we have dynamically resolved the motions of the dominant cool atmospheric component discovered in alpha Ori from multi-wavelength radio interferometry by Lim et al. (1998). Surprisingly, the emission centroids are quite Gaussian and at rest with respect to the M supergiants. These constraints combined with model calculations of the infrared emission line fluxes for alpha Ori imply that the warm material has a low outflow velocity and is located close to the star. We have also detected narrow [Fe I] 24.04 um emission that confirms that Fe II is the dominant ionization state in alpha Ori's extended atmosphere.Comment: 79 pages including 10 figures and 2 appendices. Accepted by Ap

Investigating the cardioprotective potential of exosomes from different cellular sources

Myocardial infarction is the leading cause of mortality worldwide. Reperfusion is the primary therapy for myocardial infarction. Paradoxically, reperfusion causes further cell death beyond the injury caused by ischaemia alone. Exosomes are a type of extracellular vesicles released from cells. Exosomes from stem cells have been reported to confer cardioprotection from ischaemia and reperfusion injury. However, since it is currently challenging to obtain exosomes of high purity and quantity, it is difficult to know whether exosomes or residual contaminants are responsible for cardioprotection. In this thesis, I report my studies comparing different techniques to isolate exosomes and developing a novel affinity method to isolate more pure exosomes. I show that exosomes separated by size-exclusion chromatography are not as pure as affinity-purified exosomes. I found that exosomes obtained from a commercial collaborator using a combination of by size exclusion chromatography and tangential flow filtration were highly variable. Therefore, a novel isolation method was established in which exosomes were affinity purified by immune-pulldown of an epitope tag transiently expressed in cells in culture. This method allows the collection of more pure exosomes. Exosomes purified by this method could be used to understand the role of exosomes in cardioprotection. Finally, I investigated several previously published cell models of cardiac ischaemia and reperfusion injury focusing on mitochondrial injury, but these had low replicability

Optical code-division multiple access system and optical signal processing

This thesis presents our recent researches on the development of coding devices, the investigation of security and the design of systems in the optical cod-division multiple access (OCDMA) systems. Besides, the techniques of nonlinear signal processing used in the OCDMA systems fire our imagination, thus some researches on all-optical signal processing are carried out and also summarized in this thesis. Two fiber Bragg grating (FBG) based coding devices are proposed. The first coding device is a superstructured FBG (SSFBG) using ±π/2-phase shifts instead of conventional 0/π-phase shifts. The ±π/2-phase-shifted SSFBG en/decoders can not only conceal optical codes well in the encoded signals but also realize the reutilization of available codes by hybrid use with conventional 0/π-phase-shifted SSFBG en/decoders. The second FBG based coding device is synthesized by layer-peeling method, which can be used for simultaneous optical code recognition and chromatic dispersion compensation. Then, two eavesdropping schemes, one-bit delay interference detection and differential detection, are demonstrated to reveal the security vulnerability of differential phase-shift keying (DPSK) and code-shift keying (CSK) OCDMA systems. To address the security issue as well as increase the transmission capacity, an orthogonal modulation format based on DPSK and CSK is introduced into the OCDMA systems. A 2 bit/symbol 10 Gsymbol/s transmission system using the orthogonal modulation format is achieved. The security of the system can be partially guaranteed. Furthermore, a fully-asynchronous gigabit-symmetric OCDMA passive optical network (PON) is proposed, in which a self-clocked time gate is employed for signal regeneration. A remodulation scheme is used in the PON, which let downstream and upstream share the same optical carrier, allowing optical network units source-free. An error-free 4-user 10 Gbit/s/user duplex transmission over 50 km distance is reazlied. A versatile waveform generation scheme is then studied. A theoretical model is established and a waveform prediction algorithm is summarized. In the demonstration, various waveforms are generated including short pulse, trapezoidal, triangular and sawtooth waveforms and doublet pulse. ii In addition, an all-optical simultaneous half-addition and half-subtraction scheme is achieved at an operating rate of 10 GHz by using only two semiconductor optical amplifiers (SOA) without any assist light. Lastly, two modulation format conversion schemes are demonstrated. The first conversion is from NRZ-OOK to PSK-Manchester coding format using a SOA based Mach-Zehnder interferometer. The second conversion is from RZ-DQPSK to RZ-OOK by employing a supercontinuum based optical thresholder

LLE 1994 annual report, October 1993--September 1994

This is the 1994 annual report for the University of Rochester, Laboratory for Laser Energetics. The report is presented as a series of research type reports. The titles emphasize the breadth of work carried out. They are: stability analysis of unsteady ablation fronts; characterization of laser-produced plasma density profiles using grid image refractometry; transport and sound waves in plasmas with light and heavy ions; three-halves-harmonic radiation from long-scale-length plasmas revisited; OMEGA upgrade status report; target imaging and backlighting diagnosis; effect of electron collisions on ion-acoustic waves and heat flow; particle-in-cell code simulations of the interaction of gaussian ultrashort laser pulses with targets of varying initial scale lengths; characterization of thick cryogenic fuel layers: compensation for the lens effect using convergent beam interferometry; compact, multijoule-output, Nd:Glass, large-aperture ring amplifier; atomic force microscopy observation of water-induced morphological changes in Y{sub 2}O{sub 3} monolayer coatings; observation of longitudinal acceleration of electrons born in a high-intensity laser focus; spatial intensity nonuniformities of an OMEGA beam due to nonlinear beam propagation; calculated X-ray backlighting images of mixed imploded targets; evaluation of cosmic rays for use in the monitoring of the MEDUSA scintillator-photomultiplier diagnostic array; highly efficient second-harmonic generation of ultra-intense Nd:Glass laser pulses multiple cutoff wave numbers of the ablative Rayleigh-Taylor instability; ultrafast, all-silicon light modulator; angular dependence of the stimulated Brillouin scattering in homogeneous plasma; femtosecond excited-state dynamics of a conjugated ladder polymer

An Observational Study of Molecular Dust Precursors in Circumstellar Envelopes

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 18-12-2020CSIC. Instituto de Física Fundamental (IFF

Recent Progress in Optical Fiber Research

This book presents a comprehensive account of the recent progress in optical fiber research. It consists of four sections with 20 chapters covering the topics of nonlinear and polarisation effects in optical fibers, photonic crystal fibers and new applications for optical fibers. Section 1 reviews nonlinear effects in optical fibers in terms of theoretical analysis, experiments and applications. Section 2 presents polarization mode dispersion, chromatic dispersion and polarization dependent losses in optical fibers, fiber birefringence effects and spun fibers. Section 3 and 4 cover the topics of photonic crystal fibers and a new trend of optical fiber applications. Edited by three scientists with wide knowledge and experience in the field of fiber optics and photonics, the book brings together leading academics and practitioners in a comprehensive and incisive treatment of the subject. This is an essential point of reference for researchers working and teaching in optical fiber technologies, and for industrial users who need to be aware of current developments in optical fiber research areas

Molecular complexity in envelopes of evolved stars : detailed study of the molecular emissión of the objects IK Tau, OH231.8 + 4,2 and IRC + 10216

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Astrofísica y Ciencias de la Atmósfera, leída el 09-06-2017.Las estrellas evolucionadas cuyas masas durante la secuencia principal estaban comprendidas aproximadamente entre 1 y 8 masas solares, como lo será nuestro Sol dentro de aproximadamente 4500 millones de años, son las principales responsables del enriquecimiento del medio interestelar. En la fase llamada rama asintótica de las gigantes, estas estrellas crean una envoltura a su alrededor que se forma debido a intensos procesos de pérdida de masa. Dichas envolturas están compuestas principalmente por granos de polvo y moléculas en fase gaseosa que experimentaran distintos procesos físico-químicos dando lugar a nuevas especies. Dado que las condiciones físicas en estos objetos se conocen de manera bastante precisa, resultan ser excelentes laboratorios para estudiar y comprender la complejidad molecular y la evolución química del Universo. Los procesos radiativos y colisionales que se dan en las envolturas de las estrellas evolucionadas pueden modificar el estado cuántico de las moléculas. En particular, a las temperaturas dadas (aproximadamente entre 2500 y 10 K), se producen numerosas transiciones del estado rotacional de las moléculas, que producen líneas espectrales de emisión detectables en el rango de longitud de onda milimétrico. Del análisis de estas líneas de emisión obtenemos información sobre la composición y propiedades de las envolturas. En esta tesis, se presentan los resultados obtenidos del estudio de la emisión molecular de tres envolturas circunestelares: IKTau, OH231.8+4.2 e IRC+10216. IKTau y OH231.8+4.2 son objetos ricos en oxígeno cuyas propiedades físicas están relativamente bien determinadas. Sin embargo, no se conoce el inventario molecular completo de ambas fuentes dado que hasta la fecha no han sido extensivamente estudiadas. IRC+10216 es una envoltura rica en carbono, que por sus características es la envoltura más estudiada del Universo. En el caso de las envolturas ricas en oxígeno, hemos llevado a cabo dos barridos espectrales en el rango milimétrico utilizando la antena de IRAM 30m y también observaciones de OH231.8+4.2 con el instrumento HIFI de Herschel. Este trabajo nos ha permitido obtener el inventario molecular, caracterizar las propiedades físicas de la emisión molecular, y determinar las abundancias de las moléculas presentes en ambos objetos. Respecto a IRC+10216, presentamos las primeras observaciones de alta resolución espacial obtenidas con ALMA además de otros resultados obtenidos con IRAM 30m...Evolved stars whose main sequence masses were comprised between approximately 1 and 8 solar masses, for example like our Sun will be after 4.5 billion years from now, are the main contributors to the enrichment of the interstellar medium. These stars create a circumstellar envelope around them during the asymptotic giant branch phase, which is formed due to an intense process of mass loss. Circumstellar envelopes are composed mainly of dust grains and molecules in gas phase, which are efficiently formed in the atmospheres of these stars. These compounds experience different physico-chemical processes in the circumstellar envelopes, that lead to the production of new species. Circumstellar envelopes are excellent laboratories to study the molecular complexity and the chemical evolution of the Universe. Radiative and collisional processes can modify the quantum state of the molecules present in the circumstellar envelopes of evolved stars. In particular, at the temperatures found in these objects (about 2500 K near the photosphere of the star, down to ∼10K in the outermost regions), numerous transitions occur due to the change in the rotational state of the molecules, producing emission lines detectable mainly in the millimeter wavelength range. From the analysis of these emission lines we obtain information about the composition and properties of the envelopes. The latest advances in the field of instrumentation are allowing us to observe the circumstellar envelopes of evolved stars in this range of the electromagnetic spectrum with an unprecedented sensitivity, spatial, and spectral resolution. We are in the era of ALMA, Herschel, IRAM-30m, NOEMA, and many other instruments that are motivating important discoveries, as well as changing our vision of the circumstellar envelopes and the Universe in general...Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu