Investigations of Protostellar Outflow Launching and Gas Entrainment: Hydrodynamic Simulations and Molecular Emission

We investigate protostellar outflow evolution, gas entrainment, and star formation efficiency using radiation-hydrodynamic simulations of isolated, turbulent low-mass cores. We adopt an X-wind launching model, in which the outflow rate is coupled to the instantaneous protostellar accretion rate and evolution. We vary the outflow collimation angle from $\theta$=0.01-0.1 and find that even well collimated outflows effectively sweep up and entrain significant core mass. The Stage 0 lifetime ranges from 0.14-0.19 Myr, which is similar to the observed Class 0 lifetime. The star formation efficiency of the cores spans 0.41-0.51. In all cases, the outflows drive strong turbulence in the surrounding material. Although the initial core turbulence is purely solenoidal by construction, the simulations converge to approximate equipartition between solenoidal and compressive motions due to a combination of outflow driving and collapse. When compared to a simulation of a cluster of protostars, which is not gravitationally centrally condensed, we find that the outflows drive motions that are mainly solenoidal. The final turbulent velocity dispersion is about twice the initial value of the cores, indicating that an individual outflow is easily able to replenish turbulent motions on sub-parsec scales. We post-process the simulations to produce synthetic molecular line emission maps of $^{12}$CO, $^{13}$CO, and C$^{18}$O and evaluate how well these tracers reproduce the underlying mass and velocity structure.Comment: Accepted to ApJ, 17 pages, 15 figure

Insulated conducting cantilevered nanotips and two-chamber recording system for high resolution ion sensing AFM.

Biological membranes contain ion channels, which are nanoscale pores allowing controlled ionic transport and mediating key biological functions underlying normal/abnormal living. Synthetic membranes with defined pores are being developed to control various processes, including filtration of pollutants, charge transport for energy storage, and separation of fluids and molecules. Although ionic transport (currents) can be measured with single channel resolution, imaging their structure and ionic currents simultaneously is difficult. Atomic force microscopy enables high resolution imaging of nanoscale structures and can be modified to measure ionic currents simultaneously. Moreover, the ionic currents can also be used to image structures. A simple method for fabricating conducting AFM cantilevers to image pore structures at high resolution is reported. Tungsten microwires with nanoscale tips are insulated except at the apex. This allows simultaneous imaging via cantilever deflections in normal AFM force feedback mode as well as measuring localized ionic currents. These novel probes measure ionic currents as small as picoampere while providing nanoscale spatial resolution surface topography and is suitable for measuring ionic currents and conductance of biological ion channels

An Extinction Study of the Taurus Dark Cloud Complex

We present a study of the detailed distribution of extinction in a region of the Taurus dark cloud complex. Our study uses new BVR images of the region, spectral classification data for 95 stars, and IRAS Sky Survey Atlas (ISSA) 60 and 100 micron images. We study the extinction of the region in four different ways, and we present the first inter-comparison of all these methods, which are: 1) using the color excess of background stars for which spectral types are known; 2) using the ISSA 60 and 100 micron images; 3) using star counts; and 4) using an optical (V and R) version of the average color excess method used by Lada et al. (1994). We find that all four methods give generally similar results, with important exceptions. To study the structure in the dust distribution, we compare the ISSA extinction and the extinction measured for individual stars. From the comparison, we conclude that in the relatively low extinction regions studied, with 0.9 < A_V < 3.0 mag (away from filamentary dark clouds and IRAS cores), there are no fluctuations in the dust column density greater than 45% (at the 99.7% confidence level), on scales smaller than 0.2 pc. We also report the discovery of a previously unknown stellar cluster behind the Taurus dark cloud near R.A 4h19m00s, Dec. 27:30:00 (B1950)Comment: 49 pages (which include 6 pages of tables and 6 pages of figures

Estrategias cognitivas desarrolladas por estudiantes de noveno grado para la soluci?n de problemas de combinatoria simple

65 P?ginasEsta investigaci?n tuvo como poblaci?n de estudio estudiantes de grado noveno, estudiantes que se encuentran en un rango de edad entre 13 y 15 a?os, quienes hasta el d?a de hoy no han recibido instrucci?n alguna sobre conceptos relacionados con el an?lisis combinatorio. Nuestra investigaci?n identificar? y caracterizar? las diferentes estrategias cognitivas que utilizan los estudiantes del grado 9 cuando resuelven problemas simples de combinatoria, apoyados exclusivamente en su intuici?n y su capacidad cognitiva, evidenciando c?mo los adolescentes descubren procedimientos sistem?ticos de enumeraci?n y recuentos combinatorios de manera espont?nea y sin ayuda de la instrucci?n. La investigaci?n se apoya en trabajos realizados por Carmen Batanero sobre educaci?n Estad?stica, la clasificaci?n planteada por Dubois, trabajos sobre el desarrollo cognitivo de Piaget y la Teor?a de los Campos Conceptuales de Vergnaud.ABSTRACT This research was to study population ninth year students, students who are at an age range between 13 and 15 years, who until today have not received any instruction on concepts related to combinatorial analysis. Our research will identify and characterize the different cognitive strategies used by students in grade 9 when solving simple combinatorial problems, supported solely on intuition and cognition, demonstrating how teens discover systematic procedures and combinatorial enumeration counts spontaneously without aid instruction. The research is based on trabajaos made by Carmen Batanero on education statistics, silver classification Dubois, work on the cognitive development of Piaget and theory of conceptual fields of Vergnaud.INTRODUCCI?N 14 1. PLANTEAMIENTO DEL PROBLEMA 17 1.1 ANTECEDENTES. 17 1.1.1 Razonamiento Combinatorio en Alumnos de Secundaria. . 17 1.1.2 Razonamiento Combinatorio en Estudiantes con Preparaci?n Matem?tica Avanzada18 1.1.3 Modelos Combinatorios Impl?citos y Resoluci?n de Problemas en Clase de cuarto a?o. 18 1.1.4 Conteo. Una Propuesta Did?ctica y su An?lisis. 19 1.2 PREGUNTA GENERADORA 20 2. OBJETIVOS 21 2.1 OBJETIVO GENERAL 21 2.2 OBJETIVOS ESPEC?FICOS 21 3. MARCO DE REFERENCIA22 3.1 MARCO TE?RICO 22 3.1.1 La teor?a de los campos conceptuales. 22 3.1.2 Forma operatoria y forma predicativa del conocimiento 24 3.1.3 Actividad 24 3.1.4 Jean Piaget. 26 3.1.5 Efraim Fischbein. 27 4. METODOLOG?A 31 4.1 ESTRATEGIAS UTILIZADAS EN LA RESOLUCI?N DE PROBLEMAS 31 4.1.1 Descripci?n del cuestionario 31 4.2 ESTRATEGIAS GENERALES EMPLEADAS POR LOS ALUMNOS 32 4.2.1 Problema 1 33 4.2.2 Problema 2 35 4.2.3 Problema 3 37 4.2.4 Problema 4 38 4.2.5 Problema 5. 40 4.2.6 Problema 6 42 4.2.7 Problema 7. 44 4.2.8 Problema 8 46 5. CONCLUSIONES 49 REFERENCIAS 52 ANEXOS 5