The Formation of Self-Gravitating Cores in Turbulent Magnetized Clouds

We use ZEUS-MP to perform high resolution, three-dimensional, super-Alfvenic turbulent simulations in order to investigate the role of magnetic fields in self-gravitating core formation within turbulent molecular clouds. Statistical properties of our super-Alfvenic model without gravity agree with previous similar studies. Including self-gravity, our models give the following results. They are consistent with the turbulent fragmentation prediction of the core mass distribution of Padoan & Nordlund. They also confirm that local gravitational collapse is not prevented by magnetohydrodynamic waves driven by turbulent flows, even when the turbulent Jeans mass exceeds the mass in the simulation volume. Comparison of results between 256^3 and 512^3 zone simulations reveals convergence in the collapse rate. Analysis of self-gravitating cores formed in the simulation shows that: (1) All cores formed are magnetically supercritical by at least an order of magnitude. (2) A power law relation between central magnetic field strength and density B_c propto rho_c^{1/2} is observed despite the cores being strongly supercritical. (3) Specific angular momentum j propto R^{3/2} for cores with radius R. (4) Most cores are prolate and triaxial in shape, in agreement with the results of Gammie et al.Comment: 49 pages, 22 figure

Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison

Knowledge of the relative stabilities of alane (AlH3) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for thirty-eight alane complexes with NH3-nRn (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH2-nRn (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine, and obtaining upper limits of delta G for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. Based on this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system.Comment: Accepted by the Journal of Physical Chemistry

Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions

We study the formation of H2 in the ISM, using a modified version of the astrophysical magnetohydrodynamical code ZEUS-MP that includes a non-equilibrium treatment of the formation and destruction of H2. We examine two different approximations to treat the shielding of H2 against photodissociation: a local approximation, which gives us a solid lower bound on the amount of shielding, and a method based on ray-tracing that is considerably more accurate in some circumstances but that produces results that are harder to clearly interpret. Either approximation allows one to perform three-dimensional high-resolution simulations of cloud formation with only modest computational resources. We also include a detailed treatment of the thermal behaviour of the gas. In this paper, we focus on the problem of molecular cloud formation in gravitationally unstable, initially static gas. We show that in these conditions, and for initial densities consistent with those observed in the cold, neutral atomic phase of the interstellar medium, H2 formation occurs on a timescale t > 10 Myr, comparable to or longer than the gravitational free-fall timescale of the cloud. We also show that the collapsing gas very quickly reaches thermal equilibrium and that the equation of state of the gas is generally softer than isothermal. Finally, we demonstrate that although these results show little sensitivity to variations in most of our simulation parameters, they are highly sensitive to the assumed initial density n_i. Reducing n_i significantly increases the cloud formation timescale and decreases the amount of hydrogen ultimately converted to H2. (Abridged).Comment: 89 pages, 40 figures, AASTex. Results section significantly revised and extended. Includes results from a large number of new simulations performed using a treatment of H2 photodissociation based on ray-tracing. This version matches that accepted by ApJ

Wndchrm – an open source utility for biological image analysis

<p>Abstract</p> <p>Background</p> <p>Biological imaging is an emerging field, covering a wide range of applications in biological and clinical research. However, while machinery for automated experimenting and data acquisition has been developing rapidly in the past years, automated image analysis often introduces a bottleneck in high content screening.</p> <p>Methods</p> <p><it>Wndchrm </it>is an open source utility for biological image analysis. The software works by first extracting image content descriptors from the raw image, image transforms, and compound image transforms. Then, the most informative features are selected, and the feature vector of each image is used for classification and similarity measurement.</p> <p>Results</p> <p><it>Wndchrm </it>has been tested using several publicly available biological datasets, and provided results which are favorably comparable to the performance of task-specific algorithms developed for these datasets. The simple user interface allows researchers who are not knowledgeable in computer vision methods and have no background in computer programming to apply image analysis to their data.</p> <p>Conclusion</p> <p>We suggest that <it>wndchrm </it>can be effectively used for a wide range of biological image analysis tasks. Using <it>wndchrm </it>can allow scientists to perform automated biological image analysis while avoiding the costly challenge of implementing computer vision and pattern recognition algorithms.</p

The potential of urinary metabolites for diagnosing multiple sclerosis

A definitive diagnostic test for multiple sclerosis (MS) does not exist; instead physicians use a combination of medical history, magnetic resonance imaging, and cerebrospinal fluid analysis (CSF). Significant effort has been employed to identify biomarkers from CSF to facilitate MS diagnosis; however none of the proposed biomarkers have been successful to date. Urine is a proven source of metabolite biomarkers and has the potential to be a rapid, non-invasive, inexpensive, and efficient diagnostic tool for various human diseases. Nevertheless, urinary metabolites have not been extensively explored as a source of biomarkers for MS. Instead, we demonstrate that urinary metabolites have significant promise for monitoring disease-progression, and response to treatment in MS patients. NMR analysis of urine permitted the identification of metabolites that differentiate experimental autoimmune encephalomyelitis (EAE)-mice (prototypic disease model for MS) from healthy and MS drug-treated EAE mice

Redefining corporate accountability through integrated reporting: what happens when values and value creation meet?

The landscape of corporate reporting is about to change considerably. The concepts, principles, and elements that characterize the way organizations report their annual performances are currently being questioned, debated, and redesigned throughout the world. This is happening as key elements such as capital employed, value creation, and accountability are redefined in practice. What are the types of capital that an organization uses and affects? In what ways is value created and distributed over time? To whom are organizations accountable? A possible answer to these critical questions is offered by Integrated Reporting (IR), a process that results in communicating\u2014 through an annual integrated report\u2014value creation over time

Leading practices in integrated reporting: management accountants will guide their companies on the journey to value creation

Integrated Reporting (IR) is making the leap from promising concept to powerful practice. Released at the end of 2013 by the International Integrated Reporting Council (IIRC), a global coalition of regulators, investors, companies, standards setters, the accounting profession, and nongovernmental organizations (NGOs), the IR Framework has been robustly tested and piloted in 25 countries. As we described in the article \u201cRedefining Corporate Accountability through Integrated Reporting\u201d (Strategic Finance, August 2013) and in our book Integrated Reporting: Concepts and Cases that Redefine Corporate Accountability (Springer, 2013), the Framework was co-created with business and investors and provides an \u201copen\u201d platform for IR to move toward the mainstream. To shed light on the way in which IR is currently being adopted and reflect on the possible opportunities ahead for management accountants and finance professionals, we will explore some leading examples of integrated reporting at Lawson, Inc.; Eni; and SAP