Observations of Small Scale ISM Structure in Dense Atomic Gas

We present high resolution (R~170,000) Kitt Peak National Observatory Co'ude Feed telescope observations of the interstellar KI 7698 angstrom line towards 5 multiple star systems with saturated NaI components. We compare the KI absorption line profiles in each of the two (or three) lines of sight in these systems, and find significant differences between the sight-lines in 3 out of the 5 cases. We infer that the small scale structure traced by previous NaI observations is also present in at least some of the components with saturated NaI absorption lines, and thus the small scale structures traced by the neutral species are occurring at some level in clouds of all column densities. We discuss the implications of that conclusion and a potential explanation by density inhomogeneities

Non-linear Preheating with Scalar Metric Perturbations

We have studied preheating of field perturbations in a 3-dimensional lattice including the effect of scalar metric perturbations, in two generic models of inflation: chaotic inflation with a quartic potential, and standard hybrid inflation. We have prepared the initial state for the classical evolution of the system with vanishing vector and tensor metric perturbations, consistent with the constraint equations, the energy and momentum constraints. The non-linear evolution inevitably generates vector and tensor modes, and this reflects on how well the constraint equations are fulfilled during the evolution. The induced preheating of the scalar metric perturbations is not large enough to backreact onto the fields, but it could affect the evolution of vector and tensor modes. This is the case in hybrid inflation for some values of the coupling $g$ and the height of potential $V_0^{1/4}$. For example with $V_0^{1/4} \simeq 10^{15}$ GeV, preheating of scalar perturbations is such that their source term in the evolution equation of tensor and vector becomes comparable to that of the field anisotropic stress.Comment: 15 pages, 12 eps figure

An extension problem for the CR fractional Laplacian

We show that the conformally invariant fractional powers of the sub-Laplacian on the Heisenberg group are given in terms of the scattering operator for an extension problem to the Siegel upper halfspace. Remarkably, this extension problem is different from the one studied, among others, by Caffarelli and Silvestre.Comment: 33 pages. arXiv admin note: text overlap with arXiv:0709.1103 by other author

Small-Scale Interstellar Na I Structure Toward M92

We have used integral field echelle spectroscopy with the DensePak fiber-optic array on the KPNO WIYN telescope to observe the central 27" x 43" of the globular cluster M92 in the Na I D wavelength region at a spatial resolution of 4". Two interstellar Na I absorption components are evident in the spectra at LSR velocities of 0 km/s (Cloud 1) and -19 km/s (Cloud 2). Substantial strength variations in both components are apparent down to scales limited by the fiber-to-fiber separations. The derived Na I column densities differ by a factor of 4 across the Cloud 1 absorption map and by a factor of 7 across the Cloud 2 map. Using distance upper limits of 400 and 800 pc for Cloud 1 and Cloud 2, respectively, the absorption maps indicate structure in the ISM down to scales of 1600 and 3200 AU. The fiber-to-fiber Na I column density differences toward M92 are comparable to those found in a similar study of the ISM toward the globular cluster M15. Overall, the structures in the interstellar components toward M92 have significantly lower column densities than those toward M15. We interpret these low column density structures as small-scale turbulent variations in the gas and compare them to the larger-scale, higher column density variations toward M15, which may be the hallmarks of actual H I structures.Comment: 9 pages, 2 figures, accepted for publication in ApJ Letter

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Lignocellulosic biomass is an abundant, rich source of aromatic compounds, but direct utilization of raw lignin has been hampered by both the high heterogeneity and variability of linking bonds in this biopolymer. Ab initio steered molecular dynamics (AISMD) has emerged both as a fruitful direct computational screening approach to identify products that occur through mechanical depolymerization (i.e., in sonication or ball-milling) and as a sampling approach. By varying the direction of force and sampling over 750 AISMD trajectories, we identify numerous possible pathways through which lignin depolymerization may occur in pyrolysis or through catalytic depolymerization as well. Here, we present eight unique major depolymerization pathways discovered via AISMD for the recently characterized spirodienone lignin branching linkage that may comprise around 10% weight of all lignin in some softwoods. We extract representative trajectories from AISMD and carry out reaction pathway analysis to identify energetically favorable pathways for lignin depolymerization. Importantly, we identify dynamical effects that could not be observed through more traditional calculations of bond dissociation energies. Such effects include thermodynamically favorable recovery of aromaticity in the dienone ring that leads to near-barrierless subsequent ether cleavage and hydrogen bonding effects that stabilize newly formed radicals. Some of the most stable spirodienone fragments that reside at most 1 eV above the reactant structure are formed with only 2 eV barriers for C-C bond cleavage, suggesting key targets for catalyst design to drive targeted depolymerization of lignin.National Science Foundation (U.S.) (Grant ECCS1449291)Massachusetts Institute of Technology (Research Support Corporation Reed Grant)Burroughs Wellcome Fund (Career Award at the Scientific Interface

Low-Metallicity Gas Clouds in a Galaxy Proto-Cluster at Redshift 2.38

We present high resolution spectroscopy of a QSO whose sight-line passes through the halo of a pair of elliptical galaxies at redshift 2.38. This pair of galaxies probably lies at the center of a galaxy proto-cluster, and is embedded in a luminous extended Ly-alpha nebula. The QSO sight-line intersects two small gas clouds within this halo. These clouds have properties similar to those of high velocity clouds (HVCs) seen in the halo of the Milky Way. The gas is in a cool (< 2 x 10^4 K) and at least 20% neutral phase, with metallicities in the range -3.0 < [Fe/H] < -1.1 and neutral hydrogen column densities of ~10^19.5 /cm^2. The origin of these clouds is unclear. The presence of low metallicity gas within this possible proto-cluster implies either that the intra-cluster medium has not been enriched with metals at this redshift, or the clouds are embedded within a hot, ionized, metal-rich gas phase.Comment: Accepted to appear in ApJ Letter

Electronic tuning and uniform superconductivity in CeCoIn5

We report a globally reversible effect of electronic tuning on the magnetic phase diagram in CeCoIn_{5} driven by electron (Pt and Sn) and hole (Cd, Hg) doping. Consequently, we are able to extract the superconducting pair breaking component for hole and electron dopants with pressure and co-doping studies, respectively. We find that these nominally non-magnetic dopants have a remarkably weak pair breaking effect for a d-wave superconductor. The pair breaking is weaker for hole dopants, which induce magnetic moments, than for electron dopants. Furthermore, both Pt and Sn doping have a similar effect on superconductivity despite being on different dopant sites, arguing against the notion that superconductivity lives predominantly in the CeIn_{3} planes of these materials. In addition, we shed qualitative understanding on the doping dependence with density functional theory calculations.Comment: Accepted for publication in Phys. Rev. Lett. (October 1, 2012

El discurso narrativo y su representaci?n mediante el c?mic, una propuesta did?ctica para promover la lectura y la escritura en el grado cuarto del Gimnasio Santa Roc?o

118 p. Recurso Electr?nicoA partir de la observaci?n realizada en la instituci?n, se tom? como poblaci?n el grado cuarto donde se encontr? falencias en cuanto a la comprensi?n lectora y producci?n escrita. Se implement? la investigaci?n ?EL DISCURSO NARRATIVO Y SU REPRESENTACI?N MEDIANTE EL C?MIC, UNA PROPUESTA DID?CTICA PARA PROMOVER LA LECTURA Y LA ESCRITURA EN EL GRADO CUARTO DEL GIMNASIO SANTA ROC?O? para fortalecer la comprensi?n lectora a partir de la lectura de textos narrativos cortos que posibilit? la creaci?n de comics. Para su implementaci?n se elaboraron talleres con actividades l?dicas donde los estudiantes leyeron textos, identificaron personajes, crearon y expusieron sus propios comics para ser incluidos en el libro ?mis creaciones?. Para este proceso se tuvo en cuenta la investigaci?n cualitativa y el dise?o Investigaci?n Acci?n Participativa. De acuerdo con lo anterior se fundamenta en la normatividad emanada por las pol?ticas gubernamentales en: Ley general de educaci?n, lineamientos y est?ndares curriculares; al igual que te?ricos como Amaya (2002), C?rdenas (2004), Baena (1996), Ni?o (1985), Piaget (1973) y Ausubel (1983) que fortalecieron la conceptualizaci?n del lenguaje, la lectura, la escritura, el texto narrativo, el comic, los aspectos psicol?gicos y pedag?gicos que sirvieron como base para el desarrollo metodol?gico. En este orden de ideas se logr? que los estudiantes desarrollaran la competencia lectora, la creaci?n de textos propios a partir de vivencias y experiencias de la cotidianidad involucrado el comic como estrategia did?ctica que potencio la comprensi?n y producci?n textual. Palabras clave: Lectura, escritura, texto narrativos y comic.From the done observation at Gimnasio Santa Rocio, placed in Villa del Rio neighbourhood in the seventh district of Bosa. Some students of grade fourth were taken, which shawed some difficulties in reading comprehension and written production implemented an investigation called the narrative speech and its representation throught comics, a didactic proporsal to promote reading and writing in grade fourth in Gimnasio Santa Rocio aiming reinforcing reading comprehension from short narrative texts (fables and tales) those allowed to create comics. For its implementation some workshops and ludic activities were implemented; where students read text, identified characters, created and introduced their own comics to be included into the book ?My creations?. For this process it was taken into account the qualitative investigation and the participatory action research design. According to that, it is based in the rules issued by the government policies in general law of education (Ley general de Educaci?n), Curricular Guidelines (Lineamientos Curriculares) same as some theorist such as Amaya (2002), C?rdenas (2004), Baena (1996), Ni?o (1985), Vygotsky (1997), Piaget (1973) and Ausubel (1983) who strengthen the conceptualization of language, reading, writing, narrative text, comic, physiological and pedagogical aspects that were useful as a base for methodological development. In that order of ideas was achieved that students would develop the reading competence, the creations of own texts from experiences of everyday life involving comic as a didactic strategy that strength comprehension and textual production. Keywords: Reading, writing, narrative text (tales and fables) and comic