Connection between type B (or C) and F factorizations and construction of algebras

In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33 4059), we started a systematic study of the connections among different factorization types, suggested by Infeld and Hull, and of their consequences for the construction of algebras. We devised a general procedure for constructing satellite algebras for all the Hamiltonians admitting a type E factorization by using the relationship between type A and E factorizations. Here we complete our analysis by showing that for Hamiltonians admitting a type F factorization, a similar method, starting from either type B or type C ones, leads to other types of algebras. We therefore conclude that the existence of satellite algebras is a characteristic property of type E factorizable Hamiltonians. Our results are illustrated with the detailed discussion of the Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in JP

Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution

We present deep echelle spectrophotometry of the brightest emission-line knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX 4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the 3100-10420 {\AA} range. We determine electron densities and temperatures of the ionized gas from several emission-line intensity ratios for all the objects. We derive the ionic abundances of C$^{2+}$ and/or O$^{2+}$ from faint pure recombination lines (RLs) in several of the objects, permitting to derive their C/H and C/O ratios. We have explored the chemical evolution at low metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations for Galactic and extragalactic HII regions and comparing with results for halo stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy a different locus in the C/O vs. O/H diagram than those belonging to the inner discs of spiral galaxies, indicating their different chemical evolution histories, and that the bulk of C in the most metal-poor extragalactic HII regions should have the same origin than in halo stars. The comparison between the C/O ratios in HII regions and in stars of the Galactic thick and thin discs seems to give arguments to support the merging scenario for the origin of the Galactic thick disc. Finally, we find an apparent coupling between C and N enrichment at the usual metallicities determined for HII regions and that this coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

A review of early influences on physical activity and sedentary behaviors of preschool‐age children in high‐income countries

Purpose: Promoting physical activity (PA) is a key component of preventing and controlling childhood obesity. Despite well‐documented benefits of PA, globally, rates of PA among young children have declined over the past decades, and most children are not accruing sufficient PA daily. Helping children develop the foundation for PA habits early in life is critical for the promotion of health in childhood and prevention of chronic diseases later in life, and will ultimately promote longer and healthier lives for individuals and the general population. The purpose of this review is to provide a synthesis of current evidence on influences on PA and sedentary behaviors of preschool‐age children in high‐income countries. Design and Methods: A systematic review of three databases was performed. Studies conducted in high‐income countries and published from 2000 onward that addressed influences on PA and sedentary behaviors of preschool‐age children were identified and reviewed. Additionally, reference lists of identified articles and relevant published reviews were reviewed. Studies that met the following inclusion criteria were considered: (a) sample included preschoolers (age ≤5 years); (b) PA and/or sedentary behaviors or factors associated with PA and/or sedentary behaviors was assessed; (c) published in English; (d) used either quantitative or qualitative methods; and (e) conducted in a high‐income country. Data were extracted from selected studies to identify influences on PA and sedentary behaviors of preschool‐age children and organized using the social–ecological model according to multiple levels of influence. Results: Results from included studies identify multiple factors that influence PA and sedentary behaviors of young children in high‐income countries at the various levels of the social–ecological model including intrapersonal, interpersonal, environmental, organizational, and policy. Practice Implications: Given pediatric nurses’ role as primary care providers, and their frequent and continued contact with parents and their children throughout childhood through well‐child visits, immunization, and minor acute illnesses, they are well positioned to promote and support the development of early healthful PA habits of children starting in early childhood

Association between COX-2 rs 6681231 Genotype and Interleukin-6 in Periodontal Connective Tissue. A Pilot Study

This study was partially undertaken at the UCL Eastman Dental Institute, which received a proportion of funding from the Department of Health’s National Institute of Health Research (NIHR) Biomedical Research Centres funding scheme

Correlación entre la microestructura y las frecuencias de resonancia en copas de vidrio: una manera de control de calidad en los procesos de fabricación

In this work is presented a study of the resonancefrequencies and the microstructure of a setof wineglasses corresponding to a determinedproduction lot obtained from the fabrication processesof an enterprise. Considering the fracture regionsobtained when the wineglasses were in resonance,measurements of grain size, thickness and porositywere made in the zones where the fractures tookplace and where they didn’t. A correlation betweenthe microstructure and the resonance frequenciesobtained for each one of the cases are presented.And from the analysis of the signals acquiredwith computational methods, the correspondencebetween the resonance frequencies and the differentvibration modes existing in the research were studied.En este trabajo se presenta un estudio de lasfrecuencias de resonancia y la microestructura deun conjunto de copas de vidrio correspondientea un lote de producción determinado, obtenidoa partir de los procesos de fabricación de unaempresa. Teniendo en cuenta las regiones de fracturaproducidas cuando las copas entran en resonancia, serealizaron mediciones de tamaño de grano, espesor yporosidad en cada una de las fracturas y en las demászonas que no sufrieron alteración. Se presenta unacorrelación entre la microestructura y las frecuenciasde resonancia obtenidas para cada caso. A partir delanálisis de las señales, adquiridas por programas decómputo, se estudió la correspondencia entre lasfrecuencias de resonancia y los distintos modos devibración presente en el experimento