High-Resolution NIR Observations of the Circumstellar Disk System in the Bok Globule CB 26

We report on results of near-infrared and optical observations of the mm disk embedded in the Bok globule CB 26 (Launhardt & Sargent 2001). The near-infrared images show a bipolar reflection nebula with a central extinction lane which coincides with the mm disk. Imaging polarimetry of this object yielded a polarization pattern which is typical for a young stellar object surrounded by a large circumstellar disk and an envelope, seen almost edge-on. The strong linear polarization in the bipolar lobes is caused by single scattering at dust grains and allowed to locate the illuminating source which coincides with the center of the mm disk. The spectral energy distribution of the YSO embedded in CB 26 resembles that of a ClassI source with a luminosity of 0.5 L_sun.Using the pre-main-sequence evolutionary tracks and the stellar mass inferred from the rotation curve of the disk, we derive an age of the system of <10^6 yr. H_alpha and [SII] narrow-band imaging as well as optical spectroscopy revealed an Herbig-Haro object 6.15 arcmin northwest of CB 26 YSO 1, perfectly aligned with the symmetry axis of the bipolar nebula. This Herbig-Haro object (HH 494) indicates ongoing accretion and outflow activity in CB 26 YSO 1. Its excitation characteristics indicate that the Herbig-Haro flow is propagating into a low-density environment. We suggest that CB 26 YSO 1 represents the transition stage between embedded protostellar accretion disks and more evolved protoplanetary disks around T Tauri stars in an undisturbed environment.Comment: 21 pages, 6 figures (reduced resolution), ApJ accepte

Eigenvalue Bounds on Restrictions of Reversible Nearly Uncoupled Markov Chains

AbstractIn this paper we analyze decompositions of reversible nearly uncoupled Markov chains into rapidly mixing subchains. We state upper bounds on the 2nd eigenvalue for restriction and stochastic complementation chains of reversible Markov chains, as well as a relation between them. We illustrate the obtained bounds analytically for bunkbed graphs, and furthermore apply them to restricted Markov chains that arise when analyzing conformation dynamics of a small biomolecule

Analysis of the inner collection efficiency in hybrid silicon solar cells

The collection of photogenerated carriers in hybrid silicon solar cells structures were determined by the DICE (dynamic inner collection efficiency) technique. The hybrid solar cells have a microcrystalline n-type emitter and a crystalline p-type base. Cells with amorphous buffers of several thickness and p+ back surface field microcrystalline layers were also studied. Spectral response and reflectivity were measured for each sample in order to obtain the internal spectral response or quantum efficiency. These data are the input to DICE analysis, together with the optical parameters of each layer. We observed that the emitter thickness is the most important parameter which defines the solar cell photovoltaic behavior. DICE profiles show that cells with emitter thickness of 80 Å have better collection efficiency than cells with higher thickness values mainly near the surface (until 1 μm below the ITO/microcrystalline interface). The efficacy of the back surface field can be observed with this technique by determining the DICE values near the back metalization and the minority carriers diffusion length can be calculated using the DICE profile in the bulk.The collection of photogenerated carriers in hybrid silicon solar cells structures were determined by the DICE (dynamic inner collection efficiency) technique. The hybrid solar cells have a microcrystalline n-type emitter and a crystalline p-type base. Cells with amorphous buffers of several thickness and p+ back surface field microcrystalline layers were also studied. Spectral response and reflectivity were measured for each sample in order to obtain the internal spectral response or quantum efficiency. These data are the input to DICE analysis, together with the optical parameters of each layer. We observed that the emitter thickness is the most important parameter which defines the solar cell photovoltaic behavior. DICE profiles show that cells with emitter thickness of 80 Å have better collection efficiency than cells with higher thickness values mainly near the surface (until 1 μm below the ITO/microcrystalline interface). The efficacy of the back surface field can be observed with this technique by determining the DICE values near the back metalization and the minority carriers diffusion length can be calculated using the DICE profile in the bulk.The collection of photogenerated carriers in hybrid silicon solar cells structures were determined by the DICE (dynamic inner collection efficiency) technique. The hybrid solar cells have a microcrystalline n-type emitter and a crystalline p-type base. Cells with amorphous buffers of several thickness and p+ back surface field microcrystalline layers were also studied. Spectral response and reflectivity were measured for each sample in order to obtain the internal spectral response or quantum efficiency. These data are the input to DICE analysis, together with the optical parameters of each layer. We observed that the emitter thickness is the most important parameter which defines the solar cell photovoltaic behavior. DICE profiles show that cells with emitter thickness of 80 Å have better collection efficiency than cells with higher thickness values mainly near the surface (until 1 μm below the ITO/microcrystalline interface). The efficacy of the back surface field can be observed with this technique by determining the DICE values near the back metalization and the minority carriers diffusion length can be calculated using the DICE profile in the bulk

A Statistical Approach to Classification: A guide to hierarchical cluster analysis in agricultural communications research

Classification, the sorting of similar objects or organisms into groups based on shared qualities and characteristics, is how we make sense of the world. As the field of agricultural communication and our understanding of media effects becomes more complex, it is important to have approaches that allow for a valid and reliable method of classifying units of analysis — whether they are texts, people, or other artifacts — into groups based on theoretically sound variables. This paper discusses one method of classification, the hierarchical cluster analysis, and how this method may be applied by 1) Developing Variables for Study, 2) Choosing a Sample, 3) Removing Unnecessary Variables, 4) Running the analysis, and 5) Interpreting Clusters. This professional development paper suggests this method could have positive implications for agricultural and science communication research including increased validity and reliability, rigorous development, and deeper understanding of mass communication theory. In addition, we provide recommendations for future research such as audience segmentation in agricultural and science communication research

Automated Model Reduction for Complex Systems exhibiting Metastability

We present a novel method for the identification of the most important metastable states of a system with complicated dynamical behavior from time series information. The novel approach represents the effective dynamics of the full system by a Markov jump process between metastable states and the dynamics within each of these metastable states by rather simple stochastic differential equations (SDEs). Its algorithmic realization exploits the concept of hidden Markov models with output behavior given by SDEs. The numerical effort of the method is linear in the length of the given time series and quadratic in terms of the number of metastable states. The performance of the resulting method is illustrated by numerical tests and by application to molecular dynamics time series of a trialanine molecule