Completing HI observations of galaxies II. The Coma Supercluster

High sensitivity 21-cm HI line observations, with an rms noise level of \sim 0.5 mJy, were made of 35 spiral galaxies in the Coma Supercluster, using the refurbished Arecibo telescope, which resulted in the detection of 25 objects. These data, combined with the measurements available from the literature, provide the set of HI data for 94% of all late-type galaxies in the Coma Supercluster with an apparent photographic magnitude m_p <15.7 mag. We confirm that the typical scale of HI deficiency around the Coma cluster is 2 Mpc, i.e. one virial radius. Comparing the HI mass function (HIMF) of cluster with non-cluster members of the Coma Supercluster we detect a shortage of high HI mass galaxies among cluster members that can be ascribed to the pattern of HI deficiency found in rich clusters.Comment: 16 pages, 8 figures, 4 tables. Accepted for publication on A&

Managing Large Scale Project Analysis Teams through a Web Accessible Database

Large scale space programs analyze thousands of requirements while mitigating safety, performance, schedule, and cost risks. These efforts involve a variety of roles with interdependent use cases and goals. For example, study managers and facilitators identify ground-rules and assumptions for a collection of studies required for a program or project milestone. Task leaders derive product requirements from the ground rules and assumptions and describe activities to produce needed analytical products. Disciplined specialists produce the specified products and load results into a file management system. Organizational and project managers provide the personnel and funds to conduct the tasks. Each role has responsibilities to establish information linkages and provide status reports to management. Projects conduct design and analysis cycles to refine designs to meet the requirements and implement risk mitigation plans. At the program level, integrated design and analysis cycles studies are conducted to eliminate every 'to-be-determined' and develop plans to mitigate every risk. At the agency level, strategic studies analyze different approaches to exploration architectures and campaigns. This paper describes a web-accessible database developed by NASA to coordinate and manage tasks at three organizational levels. Other topics in this paper cover integration technologies and techniques for process modeling and enterprise architectures

The dependence of HII region properties on global and local surface brightness within galaxy discs

Using B, R, and H-alpha images of roughly equal-sized samples of low surface brightness (LSB) and high surface brightness (HSB) galaxies (~40 galaxies apiece), we have explored the dependence of HII region properties on local and global disc surface brightness. We have done this by constructing co-added HII region luminosity functions (LFs) according to local and central disc surface brightness and fitting Schechter functions to these LFs. The results show that the shape of the HII region LF within LSB galaxies does not change noticeably as different limiting (i.e., mu>mu_lim) local surface brightness values are used. However, the LFs for HSB galaxies have larger values of L_* and are less steep at the faint-end than those of LSB galaxies for limiting B-band local surface brightness values as faint as mu_B,lim~23-24. Both the LFs and the data for individual HII regions show that luminous (log L>39 ergs/s) HII regions are much more common within HSB discs than within LSB discs, implying that the newly formed star clusters are also larger. Taking this into account along with the results of Monte Carlo simulations, the shapes of the LFs imply that the regions within LSB discs and those within the LSB areas of HSB discs are relatively old (~5 Myr) while the regions within HSB discs for mu_B<24 are significantly younger (<1 Myr). Since the majority of the LSB galaxies do not have noticeable spiral arms and the majority of the HSB galaxies do, this may indicate a transition within HSB discs from spiral arm-driven star formation to a more locally driven, possibly sporadic form of star formation at mu_B~24, a transition that does not appear to occur within LSB discs.Comment: Accepted to MNRA

Toward the total synthesis of spirastrellolide A. Part 3: Intelligence gathering and preparation of a ring-expanded analogue

Different methods for the formation of the C.25–C.26 bond of spirastrellolide A (1) are evaluated that might qualify for the end game of the projected total synthesis, with emphasis on metathetic ways to forge the macrocyclic frame

B-Alkyl Suzuki couplings for the stereoselective synthesis of substituted pyrans

Unprotected homoallylic alcohols can be directly converted to cis-2,6-disubstituted pyrans by palladium catalyzed B-alkyl Suzuki coupling and subsequent Michael addition

The Energy of a Plasma in the Classical Limit

When \lambda_{T} << d_{T}, where \lambda_{T} is the de Broglie wavelength and d_{T}, the distance of closest approach of thermal electrons, a classical analysis of the energy of a plasma can be made. In all the classical analysis made until now, it was assumed that the frequency of the fluctuations \omega << T (k_{B}=\hbar=1). Using the fluctuation-dissipation theorem, we evaluate the energy of a plasma, allowing the frequency of the fluctuations to be arbitrary. We find that the energy density is appreciably larger than previously thought for many interesting plasmas, such as the plasma of the Universe before the recombination era.Comment: 10 pages, 2 figures, accepted for publication in Phys.Rev.Let