A simple two-component model for the far-infrared emission from galaxies

A simple model was constructed to calculate the far-infrared emission of galaxies made up of a disk component containing cool dust heated by the general interstellar radiation field and of a molecular cloud component containing warm dust heated by recently formed massive stars. This model is fitted to the optical and far-infrared data of 120 Shapley-Ames galaxies and of 20 optically studied mini-survey galaxies, resulting in the determination of blue face-on extinctions and of the total luminosities of recently born massive stars and disk stars. The ratio of these two luminosities is a more reliable star formation activity index than the previously used ratio L sub IR/L sub B. The results show that infrared selected galaxies are on the average almost three times more dusty than optically selected ones. Only about 10% of the mini-survey galaxies exhibits strongly enhanced star formation

Three-body model calculations for 16C nucleus

We apply a three-body model consisting of two valence neutrons and the core nucleus $^{14}$C in order to investigate the ground state properties and the electronic quadrupole transition of the $^{16}$C nucleus. The discretized continuum spectrum within a large box is taken into account by using a single-particle basis obtained from a Woods-Saxon potential. The calculated B(E2) value from the first 2$^+$ state to the ground state shows good agreement with the observed data with the core polarization charge which reproduces the experimental B(E2) value for $^{15}$C. We also show that the present calculation well accounts for the longitudinal momentum distribution of $^{15}$C fragment from the breakup of $^{16}$C nucleus. We point out that the dominant ($d_{5/2})^2$ configuration in the ground state of $^{16}$C plays a crucial role for these agreement.Comment: 5 pages, 3 figures, 3 table

Counterterms in Gravity in the Light-Front Formulation and a D=2 Conformal-like Symmetry in Gravity

In this paper we discuss gravity in the light-front formulation (light-cone gauge) and show how possible counterterms arise. We find that Poincare invariance is not enough to find the three-point counterterms uniquely. Higher-spin fields can intrude and mimic three-point higher derivative gravity terms. To select the correct term we have to use the remaining reparametrization invariance that exists after the gauge choice. We finally sketch how the corresponding programme for N=8 Supergravity should work.Comment: 26 pages, references added, published versio

Large-angle scattering and quasi-elastic barrier distributions

We study in detail the barrier distributions extracted from large-angle quasi-elastic scattering of heavy ions at energies near the Coulomb barrier. Using a closed-form expression for scattering from a single barrier, we compare the quasi-elastic barrier distribution with the corresponding test function for fusion. We examine the isocentrifugal approximation in coupled-channels calculations of quasi-elastic scattering and find that for backward angles, it works well, justifying the concept of a barrier distribution for scattering processes. This method offers an interesting tool for investigating unstable nuclei. We illustrate this for the $^{32}$Mg + $^{208}$Pb reaction, where the quadrupole collectivity of the neutron-rich $^{32}$Mg remains to be clarified experimentally.Comment: 26 pages, 10 eps figure

Expression of \u3cem\u3eRhizobium leguminosarum\u3c/em\u3e CFN42 Genes for Lipopolysaccharide in Strains Derived from Different \u3cem\u3eR. leguminosarum\u3c/em\u3e Soil Isolates

Two mutant derivatives of Rhizobium leguminosarum ANU843 defective in lipopolysaccharide (LPS) were isolated. The LPS of both mutants lacked O antigen and some sugar residues of the LPS core oligosaccharides. Genetic regions previously cloned from another Rhizobium leguminosarum wild-type isolate, strain CFN42, were used to complement these mutants. One mutant was complemented to give LPS that was apparently identical to the LPS of strain ANU843 in antigenicity, electrophoretic mobility, and sugar composition. The other mutant was complemented by a second CFN42 lps genetic region. In this case the resulting LPS contained O-antigen sugars characteristic of donor strain CFN42 and reacted weakly with antiserum against CFN42 cells, but did not react detectably with antiserum against ANU843 cells. Therefore, one of the CFN42 lps genetic regions specifies a function that is conserved between the two R. leguminosarum wild-type isolates, whereas the other region, at least in part, specifies a strain-specific LPS structure. Transfer of these two genetic regions into wild-type strains derived from R. leguminosarum ANU843 and 128C53 gave results consistent with this conclusion. The mutants derived from strain ANU843 elicited incompletely developed clover nodules that exhibited low bacterial populations and very low nitrogenase activity. Both mutants elicited normally developed, nitrogen-fixing clover nodules when they carried CFN42 lps DNA that permitted synthesis of O-antigen-containing LPS, regardless of whether the O antigen was the one originally made by strain ANU843

Instability of a tidal mixing front in the presence of realistic tides and mixing

Instability and lateral eddy fluxes associated with a tidal mixing front are studied using idealized primitive equation numerical model runs. The front itself develops as a result of turbulence associated with imposed tidal currents over a sloping bottom. Thus, the model includes realistic levels of turbulence and time-dependence in the base-state conditions. In all of the 21 configurations considered, the front is unstable to fluctuations that usually draw energy primarily from the potential energy pool. Scalings are developed to parameterize a) the location of the tidal mixing front; b) the eddy kinetic energy; and c) the lateral eddy coefficients. In all cases, baroclinic instability enhances the lateral mixing relative to the two-dimensional case, but the extent of enhancement varies with the input parameters. Preliminary model runs that include a simple nutrient-phytoplankton-zooplankton-detritus biological model do not suggest any substantial ecological effect of the baroclinic instabilities. The lack of a strong biological effect, despite the enhanced eddy transports, occurs because of the near cancelation of oppositely directed cross-isobath eddy fluxes in the upper and lower parts of the water column. Similarly, shallow and deep cross-frontal eddy heat fluxes also nearly balance: this cancelation appears to help explain how the classical one-dimensional potential energy criterion for frontal location can work so well in a complex ocean

Baroclinic instability of an idealized tidal mixing front

Tidal mixing fronts separate vertically homogenized waters from stratified ambient waters. The linear and nonlinear baroclinic stability of an idealized tidal mixing front is treated here in the parameter range that is stable with regard to symmetric instabilities and that has no bottom friction. All model configurations considered are unstable, and the dependence on bottom slope, stratification and other parameters is similar to that suggested by models (such as that of Blumsack and Gierasch, 1972) with much simpler configurations. The finite-amplitude evolution of the instabilities is treated using a primitive equation numerical model. The initial length scale and growth rate of the instabilities are well predicted by the linear calculations. As the system evolves, gravitational potential energy is transferred to eddy kinetic energy, which peaks at about the time that potential energy stops decreasing. The peak eddy kinetic energy depends strongly on the bottom slope, with the greatest values occurring when the bottom and near-bottom isopycnals slope in the same direction. As the fields continue to evolve, eddy kinetic energy decreases, mean kinetic energy increases, and the eddies become larger and more barotropic. The horizontal eddy mixing coefficient is estimated at the time of maximum lateral heat flux and is found to be sensitive to the magnitude of the bottom slope but not its sign. Overall, the instability and the related eddy mixing are strong enough to encourage the idea that these instabilities might be effective at a more realistic tidal mixing front

Teachers\u27 Perceived Understanding of Formative Assessment And How This Understanding Impacts Their Own Classroom Instruction

The key purpose of this qualitative case study was to gain an understanding of classroom teachers’ perceptions of the process and impact of formative assessment on classroom instruction in a secondary school. The study was designed to obtain information about how teachers view formative assessment as part of their everyday planning and preparation, as well as sought to determine whether or not there was a correlation between teachers’ perceived understanding of formative assessment and their implementation of formative assessment in the classroom. The three main research questions that guided this study were: 1) How do teachers’ perceptions of their own understanding of formative assessment affect their instructional practice? 2) How do teachers’ perceptions of their own understanding of formative assessment evolve over time? 3) What supports exist to help teachers implement formative assessment at the high school level? The case study focused on participants who were current 9-12 public school teachers representing mathematics, physical education, and foreign language. To triangulate the data, multiple types of data were collected from the teachers. Pre- and post-surveys, unstructured interviews, focus groups, classroom observations with participant observation notes, and logs were used to collect the data. Data was then analyzed using analysis of the pre-surveys and compared with information gained from the other data sources. Data was later analyzed using the post-survey and compared with the information from other data sources to determine individual teacher growth over time. The results from the first research question indicated that teachers understood the accountability of both teachers and students in the assessment process, but required additional support in determining how student learning becomes the basis for use of formative assessment, types of different methods used, and overall teacher competencies about formative assessment. The second research question indicated that growth occurred when professional supports were given in areas where weaknesses were identified. Initially, formative assessment was viewed by many as a means of compliance with the new teacher evaluation system. With continued professional development, teachers’ acceptance of formative assessment increased as their understanding of the process dually increased. In addition, as teachers began to see growth in student achievement, their overall acceptance of formative assessment also increased. The third and final research question indicated that supports must not only be global in nature, but must also be focused on the individual. When teachers know where they are and know the target of where they want or need to be, instructional growth does occur. Supports for teacher instructional practice will vary based on identified needs, understanding of formative assessment, and the type of supports available. Recommendations for follow-up study include the use of additional focus groups, extending the formative assessment survey to include lengthening the time of the study, and a change in setting to avoid certain nuances that can occur with studying the same school district. Additionally, research should be completed on the long-term effects of personalized professional development and whether teachers continue to use formative assessment practices as they gain more extensive experience. Since this particular school was undergoing a complete system change while the study was being completed, it would be dually important to investigate a school that was not in the midst of such a change. With all the additional supports available to the teachers in this study, it is important to see if a teacher’s perceived understanding of formative assessment would continue to translate into instructional practice if whole school and individual supports were not as prevalent