N-heterocyclic germylenes: structural characterisation of some heavy analogues of the ubiquitous N-heterocyclic carbenes

The X-ray crystal structures of three N-heterocyclic germylenes (NHGes) have been elucidated including the previously unknown 1,3-bis(2,6-dimethylphenyl)diazagermol-2-ylidene (1). In addition, the X-ray crystal structures of the previously synthesised 1,3-bis(2,4,6-trimethylphenyl)diazagermol-2-ylidene (2) and 1,3-bis(2,6-diisopropylphenyl)diazagermol-2-ylidene (3) are also reported. The discrete molecular structures of compounds 1 to 3 are comparable, with Ge-N bond lengths in the range 1.835-1.875 Å, while the N-Ge-N bond angles range between 83.6 and 85.2°. Compound 2 was compared to the analogous N-heterocyclic carbene species, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes). The major geometrical difference observed, as expected, was the bond angle around the divalent group 14 atom. The N-Ge-N bond angle was 83.6° for compound 2 versus the N-C-N bond angle of 101.4° for IMes. The Sn equivalent of (1), 1,3-bis(2,6-dimethylphenyl)diazastannol-2-ylidene (4), has also been synthesised and its crystal structure is reported here. In order to test their suitability as ligands, compounds 1 to 3 were reacted with a wide range of transition metal complexes. No NHGes containing metal complexes were observed. In all cases the NHGe either degraded or gave no reaction

Is participation prevention? A blurring of discourses in children's preventative initiatives in the UK

This article explores the relationships between two key concepts that have defined recent social policy initiatives for children in the UK: participation and prevention from social exclusion. Drawing on the Children's Fund initiative as an example, the article traces the diverse and sometimes contradictory discourses of childhood and social inclusion/ exclusion in stakeholders' differing rationales for supporting children's participation and prevention. The authors argue that the blurring of the rationales for participation and prevention has implications for the strategies and practices that agencies adopt and raises questions about which groups benefit and whose agendas are served by participation and prevention activities

Study of aircraft position fixing using the Navy navigational satellite system

Supersonic aircraft position fixing based on Navy navigation satellite syste

Self-Assessment and Student Improvement in an Introductory Computer Course at the Community College-level

The purpose of this study was to determine a student‟s computer knowledge upon course entry and if there was a difference in college students‟ improvement scores as measured by the difference in pretest and posttest scores of new or novice users, moderate users, and expert users at the end of a college-level introductory computing class. This study also determined whether there were differences in improvement scores by gender or age group. The results of this study were used to determine whether there was a difference in improvement scores among the 3 campus locations participating in this study. Four hundred sixty-nine students participated in this study at a community college located in Northeast Tennessee. A survey, pretest, and posttest were administered to students in a collegelevel introductory computing class. The survey consisted of demographic data that included gender, age category, location, Internet access, educational experience, and the self-rated user category, while the pretest and posttest explored the student‟s knowledge of computer terminology, hardware, the current operating system, Microsoft Word, Microsoft Excel, and Microsoft PowerPoint. The data analysis revealed significant differences in pretest scores between educational experience categories. In each instance, the pretest mean for first semester freshmen students was lower than second semester freshmen and sophomores. The study also reported significant differences between the self-rated user categories and pretest scores as well as differences in improvement scores (posttest scores minus pretest scores), which were higher for new or novice users. Of the 3 participating campus locations, students at Location 1 earned higher improvement scores than did students at Location 2. The results also indicated that there was a significant difference between the types of course delivery and course improvement scores (posttest scores minus pretest scores). The improvement scores for on ground delivery was 5 points higher than the hybrid course delivery. Finally, the gender and age categories as compared to the self-rated user categories revealed no significant differences in the study

Estuarine Oiling Increases A Long-Term Decline In Mussel Growth*

The ribbed mussel, Geukensia granosissima, cycles nutrients, contributes to soil stability, and can be a major component of predator-prey communities in salt marshes. Mussels were exposed to the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, and salt marshes remain contaminated eight years later. We hypothesized that the oiled mussels had reduced annual growth, altered population size frequency, and perhaps changed valve morphometrics. We sampled 10 marshes near Port Sulphur, LA, to measure the morphometrics of 133 mussels and their age-specific growth rate, and also the marsh oil content and percent vegetative cover. The relationships between valve weight, length and biomass weight were stable as mussels aged. A Year 1 growth decline from 1994 to 2018 is not easily explained by estuarine acidification, flooding, and temperature rise; freshening of estuarine waters is suggested to be a probable causal factor in the declining growth rate. The average valve length and dry biomass per valve declined with oiling in 2010. A multiple regression equation using the percent cover and oil concentration in 2018 described 70% of the variation in valve length. Sites with the highest oiling had few mussels with 14 annual growth bands and more of the younger mussels compared to sites with the lowest oiling. Valve growth in Year 1 declined for four years after the oil spill and was not compensated by higher growth rates in older mussels. Annual growth was below the amount predicted in a regression equation for the five years after the oil spill. Mussel populations may also have been structured by predators that were also responsive to oiling in subtle ways

The late Cretaceous environment of the Arctic: A quantitative reassessment based on plant fossils

Late Cretaceous megafossil floras from the palaeo-Arctic of northeastern Russia and northern Alaska are reviewed in respect of their age, composition, structure and floral dynamics. Palaeofloral correlations and comparisons are made between the two regions. Nine angiosperm-rich, predominantly Cenomanian to Coniacian, floras from the palaeo-Arctic are re-evaluated using Climate Leaf Analysis Multivariate Program (CLAMP) calibrated using a global gridded (0.5° x 0.5°) climate data set derived from that used in climate modelling. Additional floras from lower palaeolatitudes were used to derive latitudinal temperature gradients: seven from N. America, five from around 30 °N palaeolatitude in Europe and one from Kazakhstan. The Arctic climatic determinations, similar to previous estimates, support the existence of a northern Pacific Ocean cold gyre and a warm Arctic Ocean. At palaeolatitudes greater than 80°N floras are insufficiently diverse in woody dicot taxa to use CLAMP, but using CLAMP-derived latitudinal temperature gradients Arctic Ocean coastal environments at 70 Ma and 82°N, and which supported a diverse dinosaur magafauna, are predicted to have experienced a mean annual temperature of 6.3 ± 2.2°C, a warm month mean of 14.5 ± 3.1°C and a cold month mean no colder than -2.0 ± 3.9°C. All uncertainties are 2σ. The new estimates are in good agreement with a wide range of non-palaeobotanical climate proxies and render as an outlier warmer temperature estimates for the Arctic Ocean derived from the TEX86 proxy. Modelling, however, shows that land to ocean temperature gradients could have been steep. The CLAMP estimates also suggest high values for humidity and precipitation consistent with sedimentological indicators and, coupled with warm temperatures, support the existence of a persistent polar cloud cap that helped maintain high terrestrial air temperatures throughout prolonged periods (up to 5 months) of winter darkness

The implicit construction of multiplicity lists for classes of trees and verification of some conjectures

For the problem of understanding what multiplicities are possible for eigenvalues among real symmetric matrices with a given graph, constructing matrices with conjectured multiplicities is generally more difficult than finding constraining conditions. Here, the implicit function theorem method for constructing matrices with a given graph and given multiplicity list is refined and extended. In particular, the breadth of known circumstances in which the Jacobian is nonsingular is increased. This allows characterization of all multiplicity lists for binary, diametric, depth one trees. In addition the degree conjecture and a conjecture about the minimum number of multiplicities equal to 1 is proven for diametric trees. Finally, an intriguing conjecture about the eigenvalues of a matrix whose graph is a path and its submatrices is given, along with a discussion of some ides that would support a proof of the degree conjecture and the minimum number of 1\u27s conjecture, in general. (c) 2012 Elsevier Inc. All rights reserved

Particle acceleration in tangential discontinuities by lower hybrid waves

We consider the role that the lower-hybrid wave turbulence plays in providing the necessary resistivity at collisionless reconnection sights. The mechanism for generating the waves is considered to be the lower-hybrid drift instability. We find that the level of the wave amplitude is sufficient enough to heat and accelerate both electrons and ions