Star Cluster Survival in Star Cluster Complexes under Extreme Residual Gas Expulsion

After the stars of a new, embedded star cluster have formed they blow the remaining gas out of the cluster. Especially winds of massive stars and definitely the on-set of the first supernovae can remove the residual gas from a cluster. This leads to a very violent mass-loss and leaves the cluster out of dynamical equilibrium. Standard models predict that within the cluster volume the star formation efficiency (SFE) has to be about 33 per cent for sudden (within one crossing-time of the cluster) gas expulsion to retain some of the stars in a bound cluster. If the efficiency is lower the stars of the cluster disperse mostly. Recent observations reveal that in strong star bursts star clusters do not form in isolation but in complexes containing dozens and up to several hundred star clusters, i.e. in super-clusters. By carrying out numerical experiments for such objects placed at distances >= 10 kpc from the centre of the galaxy we demonstrate that under these conditions (i.e. the deeper potential of the star cluster complex and the merging process of the star clusters within these super-clusters) the SFEs can be as low as 20 per cent and still leave a gravitationally bound stellar population. Such an object resembles the outer Milky Way globular clusters and the faint fuzzy star clusters recently discovered in NGC 1023.Comment: 21 pages, 8 figures, accepted by Ap

Globular Clusters and Dwarf Spheroidal Galaxies

Traditionally globular clusters and dwarf spheroidal galaxies have been distinguished by using one or more of the following criteria: (1) mass, (2) luminosity, (3) size, (4) mass-to-light ratio and (5) spread in metallicity. However, a few recently discovered objects show some overlap between the domains in parameter space that are occupied by galaxies and clusters. In the present note it is shown that ellipticity can, in some cases, be used to help distinguish between globular clusters and dwarf spheroidal galaxies.Comment: MNRAS (Letters), in pres

Research on Microbiological Sterilization Problems Quarterly Report, Jul. - Sep. 1966

Microbiological sterilization studies for spacecraft decontaminatio

Capturing, using, and managing quality assurance knowledge for shuttle post-MECO flight design

Ascent initialization values used by the Shuttle's onboard computer for nominal and abort mission scenarios are verified by a six degrees of freedom computer simulation. The procedure that the Ascent Post Main Engine Cutoff (Post-MECO) group uses to perform quality assurance (QA) of the simulation is time consuming. Also, the QA data, checklists and associated rationale, though known by the group members, is not sufficiently documented, hindering transfer of knowledge and problem resolution. A new QA procedure which retains the current high level of integrity while reducing the time required to perform QA is needed to support the increasing Shuttle flight rate. Documenting the knowledge is also needed to increase its availability for training and problem resolution. To meet these needs, a knowledge capture process, embedded into the group activities, was initiated to verify the existing QA checks, define new ones, and document all rationale. The resulting checks were automated in a conventional software program to achieve the desired standardization, integrity, and time reduction. A prototype electronic knowledge base was developed with Macintosh's HyperCard to serve as a knowledge capture tool and data storage

Lower Incisors of Prairie Dogs (Cynomys) as Biorecorders of Hibernation and Season of Death

Incremental dentin and associated enamel, features visible at the surface of lower incisors of rodents, may chronicle important life-history information. This study investigated surface features of lower incisors representing 4 taxa of prairie dogs (Cynomys) in relation to hibernation and season of year. A set of abnormalities in dentin and enamel, observed on 20 of 138 incisors, always chronicled an event ending in late winter or early spring and was interpreted as a hibernation mark. Hibernation was recorded in the incisors of obligate hibernators, C. leucurus and C. gunnisoni, as well as in 20% of specimens of the facultative heterotherm, C. ludovicianus, with relevant winter growth record. Inspection of prairie dog incisors from museum collections elucidated patterns in the timing of spring emergence across species, sexes, and elevations. Growth rates of prairie dog incisors (estimated from thicknesses of circadian dentin increments) showed general seasonal patterns when pooled by sex and species, but daily growth rates recorded along individual incisors often fluctuated idiosyncratically through time. However, incisors that chronicled a significant temporal trend in daily growth rate registered either early-season (increased growth rate through time) or late-season growth (decreased growth rate through time). None of 11 late-Pleistocene fossil C. niobrarius churcherii exhibited a hibernation mark, but 4 of these exhibited significant decrease in growth rate along their incisors, probably indicating animals that died late in the active season. © 2006 American Society of Mammalogists

Estimates of Body Mass for Fossil Giant Ground Squirrels, Genus Paenemarmota

Paenemarmota Hibbard and Schultz, 1948 includes 3 species of giant ground squirrels within Marmotini (Rodentia, Sciuridae) from the Late Miocene and Pliocene of central and western North America. We developed skeletal and dental models for estimating body mass across modern species of Marmotini and apply these models to Paenemarmota. The most reliable models for estimating body mass of modern species (on the basis of length and width of femur, lengths of p4 and P4) generally yielded lower estimates of body mass for Paenemarmota than less reliable models (on the basis of lengths of m1, m2, M1, and M2). Models that were most reliable across modern species yielded 2 nonoverlapping estimates for P. barbouri Hibbard and Schultz, 1948: 9.59.8 kg on the basis of femur dimensions, and 14.416.2 kg on the basis of lengths of premolars. On the basis of lengths of premolars, P. mexicana (Wilson 1949) closely resembled P. barbouri in estimated mass (14.415.7 kg), but P. sawrockensis (Hibbard 1964) was smaller (10.012.4 kg). These large ground squirrels probably differed in mass-dependent biological attributes from all modern marmotines. © 2012 American Society of Mammalogists

Hybrid Local-Order Mechanism for Inversion Symmetry Breaking

Using classical Monte Carlo simulations, we study a simple statistical mechanical model of relevance to the emergence of polarisation from local displacements on the square and cubic lattices. Our model contains two key ingredients: a Kitaev-like orientation-dependent interaction between nearest neighbours, and a steric term that acts between next-nearest neighbours. Taken by themselves, each of these two ingredients is incapable of driving long-range symmetry breaking, despite the presence of a broad feature in the corresponding heat capacity functions. Instead each component results in a "hidden" transition on cooling to a manifold of degenerate states, the two manifolds are different in the sense that they reflect distinct types of local order. Remarkably, their intersection---\emph{i.e.} the ground state when both interaction terms are included in the Hamiltonian---supports a spontaneous polarisation. In this way, our study demonstrates how local ordering mechanisms might be combined to break global inversion symmetry in a manner conceptually similar to that operating in the "hybrid" improper ferroelectrics. We discuss the relevance of our analysis to the emergence of spontaneous polarisation in well-studied ferroelectrics such as BaTiO$_3$ and KNbO$_3$.Comment: 8 pages, 8 figure

Reproductive Biology of Blue Runner (Caranx crysos) from the Eastern Gulf of Mexico

Blue runner were obtained from commercial fisheries in south Florida, northwest Florida, and the Mississippi Delta. Monthly mean gonadosomatic indices indicated that peak spawning occurred in June, July, and August for all areas with a secondary peak in October for northwest Florida. The spawning season was confirmed for the south Florida collection by histological examination of gonads. Probit analysis of 185 northwest Florida blue runner captured during peak spawning months indicated a length-at-maturity of 267 mm. Fecundity varied from 41,000 ova in a 243·mm·FL, 288-gram fish to 1,546,000 ova in a 385·mm·FL, 1,076-gram fish. Sex ratios were 1.15F:1M for Mississippi Delta, 1.66F:1M for northwest Florida and 1.91F:1M for south Florida

Collaboration on risk management: the governance of a non-potable water reuse scheme in London

Ageing water infrastructure and population growth, issues that are characteristic of megacities, are likely to exacerbate water supply deficits in London. To address this threat, wastewater reclamation and non-potable reuse can potentially close the supply-demand gap without impacting on environmental water bodies. There is a need to understand the types of challenges that diverse stakeholders face in relation to the governance of NPR schemes, and how those challenges might be addressed in a megacity context. A case study is used to explore these challenges for an operational sewer mining scheme in London, where reclaimed non-potable water is used for irrigation and toilet flushing at the site of the London 2012 Olympic Park. Through qualitative analysis of interview and document data, the results highlight that collaboration and learning opportunities are perceived as necessary to improve scheme governance. The findings indicate that formal and informal engagement activities centred on risk management can support the development of common understandings, build important inter-stakeholder relationships and help maintain trust. Non-potable reuse can contribute to the resilience of megacities through infrastructure diversification, but its feasibility will depend on the willingness of stakeholders to participate and continually negotiate new risk management practices

Local DC electricity generated by photovoltaics (PV): Transforming the electricity infrastructure of the 21st Century

United States aging electricity infrastructure of generation, transmission and distribution facilities was built over the course of a century and is dominated by alternating current (AC). Most of the loads around us are direct current (DC) load. Commercial buildings have more than 80% DC loads. DC has many advantages over AC. Due to the advancements in power electronics today, DC infrastructure can be implemented with all the advantages of saving energy and improved reliability of the grid. By doing measurements of cell phones we will demonstrate the advantages of DC source over AC. We expect energy saving of about 25-30% by using DC in place of AC. At Edison\u27s time there was no local source of DC electricity. Today solar panels are available and the installed PV system cost is as low as $1.50 per peak watt. Due to growth of electric vehicles and grid storage, battery cost is also decreasing every day. Tesla (an electric car manufacturer) is going to build a Giga watt battery manufacturing plant in US. The combination of PV and battery storage will transform the electricity infrastructure of the 21st century