Scattering by fluffy grains

There are indications (Greenberg et al., 1988), that fluffy (i.e., porous) particles are responsible for the observed 3.4 and 10 micron emissions of comet Halley. The absorption characteristics of small particles both solid and fluffy are needed in order to explain the Halley emissions. How isolated small solid particles react to an external radiation field is well known - the Rayleigh approximation. How these same small particles emit when assembled as fluffy aggregates in another question. To what degree are the emission spectra of isolated and aggregated particles comparable. In order to quantify the assertion that fluffy particles produce the observed Halley infrared emission features, the authors are performing calculations to determine the effect of porosity on the absorption characteristics of aggregates of interstellar grain-type particles. The calculations are based on an integral representation of the scattered electromagnetic field. Results are given with application to comet Halley

Housing and labor market distortions in Poland : linkages and policy implications

Poland's housing and macroeconomic policies have restricted investments in housing and urban infrastructure to a level well below that of other European countries. This has resulted in a shortage of housing typified by 15 to 20 year waits for government sponsored housing. Shortages of this magnitude are likely to cause distortions with impacts on patterns of savings and consumption, the price level, and on the functioning of labor markets. This paper focuses particularly on how housing market distortions are transmitted to labor markets, with impacts on rates of migration, relative wage levels among different regions, and, by implication, on the productivity of the Polish work force. The basic thesis of the paper is that if housing markets are prevented from reaching their competitive equilibrium that labor markets will similarly be prevented. Evidence is examined on the extent of housing and labor market disequilibria, and estimates econometric models that relate internal migration and relative wages to alternative measures of housing market disequilibria. From these analyses it is concluded that labor markets are in fact distorted by housing market distortions, with potentially major macroeconomic costs.Banks&Banking Reform,Municipal Financial Management,Housing&Human Habitats,Public Sector Economics&Finance,Urban Housing

A comparative study of the continuum and emission characteristics of comet dust. 1: Are the silicates in Comet Halley and Kohoutek amorphous or crystalline

A continuum emission was subtracted from the 10 micron emission observed towards comets Halley and Kohoutek. The 10 micron excess emissions were compared with BN absorption and laboratory amorphous silicates. The results show that cometary silicates are predominantly amorphous which is consistent with the interstellar dust model of comets. It is concluded that cometary silicates are predominantly similar to interstellar silicates. For a periodic comet like Comet Halley, it is to be expected that some of the silicate may have been heated enough to convert to crystalline form. But apparently, this is only a small fraction of the total. A comparison of Comet Halley silicates with a combination of the crystalline forms observed in interplanetary dust particles (IPDs) seemed reasonable at first sight (Walker 1988, Brownlee 1988). But, if true, it would imply that the total silicate mass in Comet Halley dust is lower than that given by mass spectrometry data of Kissel and Krueger (1987). They estimated m sub org/m sub sil = 0.5 while using crystalline silicate to produce the 10 micron emission would give m sub org/m sub sil = 5 (Greenberg et al. 1988). This is a factor of 10 too high

La tradición musical de la sextina de Arnaut Daniel "Lo ferm voler qu'el cor m'intra" (BDT 29,14) : un artefacto lírico perfecto

Contribució al I Simposi Científic de l'IEM (Reial Acadèmia de Bones Lletres de Barcelona, 3 de juliol de 2012

Performing against the odds: developmental trajectories of children in the EPPSE 3 to 16 study

The Effective Pre-School, Primary and Secondary Education (EPPSE 3 to 16) research project is a large scale, longitudinal, mixed-methods research that is following the progress of 3,000 children since 1997 from the age of 3- to 16-years-old. A focus for EPPSE has been the extent to which pre-school, compulsory education and children’s home learning experiences (HLE) can reduce inequality. Earlier EPPSE found that what parents did with their children was important in terms of the children’s outcomes, not simply ‘who they were’ in terms of social class and income. Following a pilot study with disadvantaged children who were ‘succeeding against the odds’ towards the end of primary school, this study provides in-depth exploration and explanation of how risks and protective factors in the lives of children shape their learning life-courses, and why they lead to academic resilience for some but not for others

La gestión de incidentes críticos en la universidad

[ES] Es una mirada a los problemas universitarios desde una perspectiva aplicada, plural y bien fundamentada. Desde el primer día de clase a la jubilación se presenta una perspectiva diacrónica del devenir universitario con sus incidentes o problemas que intervienen y cambian la vida de las personas.Cantón Mayo, I. (2017). La gestión de incidentes críticos en la universidad. REDU. Revista de Docencia Universitaria. 15(1):369-371. doi:10.4995/redu.2017.5997.SWORD36937115

Mercury removal in wastewater by iron oxide nanoparticles

Mercury is one of the persistent pollutants in wastewater; it is becoming a severe environmental and public health problem, this is why nowadays its removal is an obligation. Iron oxide nanoparticles are receiving much attention due to their properties, such as: great biocompatibility, ease of separation, high relation of surface-area to volume, surface modifiability, reusability, excellent magnetic properties and relative low cost. In this experiment, Fe3O4 and γ-Fe2O3 nanoparticles were synthesized using iron salts and NaOH as precipitation agents, and Aloe Vera as stabilizing agent; then these nanoparticles were characterized by three different measurements: first, using a Zetasizer Nano ZS for their size estimation, secondly UV-visible spectroscopy which showed the existence of resonance of plasmon at λmax∼360 nm, and lastly by Scanning Electron Microscopy (SEM) to determine nanoparticles form. The results of this characterization showed that the obtained Iron oxides nanoparticles have a narrow size distribution (∼100nm). Mercury removal of 70% approximately was confirmed by atomic absorption spectroscopy measurements

Model ab initio study of charge carrier solvation and large polaron formation on conjugated carbon chains

Using long C_{N}H_{2} conjugated carbon chains with the polyynic structure as prototypical examples of one-dimensional (1D) semiconductors, we discuss self-localization of excess charge carriers into 1D large polarons in the presence of the interaction with a surrounding polar solvent. The solvation mechanism of self-trapping is different from the polaron formation due to coupling with bond-length modulations of the underlying atomic lattice well-known in conjugated polymers. Model ab initio computations employing the hybrid B3LYP density functional in conjunction with the polarizable continuum model are carried out demonstrating the formation of both electron- and hole-polarons. Polarons can emerge entirely due to solvation but even larger degrees of charge localization occur when accompanied by atomic displacements