Response of Acer saccharum seedlings to elevated O3 and CO2 concentrations

The effects of three times ambient [O3] (3x) and high [CO2] (650 µL L-1 CO2) alone and in combination were studied on 2-yr-old sugar maple (Acer saccharum) seedlings for 86 days in open top chambers. Sugar maple net CO2 assimilation rate and growth were not decreased by the O3 treatment after one growing season, and the epicuticular wax was not damaged compared with the control. The absence of response to the O3 treatment is attributable to the low stomatal conductance of this species resulting in a low O3 uptake, together with the succession of periods of high and low [O3], which allowed the seedlings to alleviate the oxidative stress. At the end of August, under high [CO2], the growth of the seedlings and net CO2 assimilation to stomatal conductance to CO2 ratio in the second flush of leaves had doubled. Under the environmental growth conditions of the chambers (high light, nutrients and water availabilities), the seedlings may benefit from the availability of CO2. Sugar maple seedlings may have a competitive growth advantage under elevated CO2 conditions and three times ambient [O3] did not decreased the fertilizing effect of CO2.[Réponse de semis d’Acer saccharum à des concentrations élevées de O3 et de CO2]Des semis d’érable à sucre de 2 ans ont été exposés en chambre à ciel ouvert pendant 86 jours à trois fois la concentration ambiante de O3 (3x) et à une forte concentration de CO2 (650 µL L-1), seul ou en combinaison. Le taux d’assimilation du CO2, la croissance des semis et les cires cuticulaires n’ont pas été modifiés par le traitement oxydatif après une saison de croissance. L’absence de réponse sous O3 est attribuée à la faible conductance stomatique de l’érable à sucre et à l’entrée réduite de O3 dans les feuilles qui en découle. De plus, l’alternance de périodes où les concentrations de O3 sont faibles et de périodes où les concentrations de O3 sont élevées a probablement permis aux semis de contrer le stress oxydatif. À la fin du mois d’août, la biomasse et le rapport assimilation nette de CO2/conductance stomatique au CO2 mesurés dans les deuxièmes pousses des semis exposés au fort CO2 ont doublé par rapport aux semis exposés au CO2 ambiant. Les conditions environnementales à l’intérieur des chambres (bonne disponibilité en lumière, éléments minéraux, eau) ont permis aux semis de profiter de la forte disponibilité en CO2. Les semis ont un avantage compétitif en termes de croissance dans les conditions environnementales de fort CO2 alors que trois fois la concentration ambiante de O3 n’a pas diminué l’effet fertilisant du fort CO2

El olvido de la lengua materna y sus consecuencias en la formación del profesorado de idiomas. Intervención y mejora de degradación de la competencia lingüística y docente del profesorado nativo

Esta Tesis Doctoral estudia el olvido - o atrición - de la lengua materna en adultos con una triple finalidad: - Analiza el concepto de atrición en la edad adulta y aclara el estado de la discusión científica sobre este fenómeno poco estudiado en España. Explica el olvido de la lengua materna (también llamada L1 o lengua primera, para distinguirla de la L2 o lengua segunda) desde un enfoque pluridisciplinar, relacionándolo con el funcionamiento cognitivo cerebral y sus mecanismos mnemónicos y situándolo en la realidad compleja del bilingüismo y plurilingüismo. - Realiza un estudio de caracterización de los efectos de la atrición, situándose en el contexto franco-español y analizando el olvido desde una perspectiva lingüística e interpretativa. Considera el olvido del idioma materno francés de una población de adultos inmersos de forma continua y prolongada en un entorno hispanohablante, tratándose de una combinación de idiomas no estudiada hasta ahora en este contexto lingüístico. Por una parte, la investigación se centra en el análisis de la producción discursiva de este público - estudiando el idioma hablado en los datos obtenidos y confrontándolo con la norma nativa francesa - y en el estudio de los comportamientos compensatorios de comunicación encontrados. Por otra parte, este trabajo explora la dimensión psicolingüística del olvido, interpretando el discurso formulado en el corpus sobre la práctica del francés en este ámbito. - Profundiza y concreta su nivel de reflexión considerando al público específico de los profesores nativos de idiomas en una posible situación de olvido de su lengua materna. Pone de manifiesto el peligro que representa la atrición en su actividad profesional y propone informar e intervenir a dos niveles diferentes (pre o post atrición), formulando respectivamente unas propuestas de actuaciones preventivas y de técnicas de apoyo y mejora de la competencia lingüística y docente de estos profesionales..

Pourquoi la connaissance du nom des lettres est-elle si importante dans l’apprentissage de la langue écrite ?

Inscrite dans le contexte théorique de la litéracie émergente, la présente recherche conduite auprès de soixante quatorze jeunes français révèle que la connaissance du nom des lettres règle les comportements d’écriture précoces et influence l’apprentissage implicite des relations lettre-phonème ainsi que le développement de la sensibilité phonémique. Parce qu’il fournit une identité phonologique aux lettres, le nom des lettres favorise la manipulation et la conceptualisation de l’écriture alphabétique. La connaissance du nom des lettres s’avère une acquisition critique, conclusion suggérant des implications pratiques pour l’enseignement préscolaire et scolaire.Situated within the theoretical context of developing literacy, this research work done with seventy-four young French students reveals that letter names knowledge sets early behaviour patterns towards writing and influences the implicit learning of letter-sound connections as well as developing phonemic awareness. As it gives a phonological identity to the letters, the names of the letters turned out to be crucial knowledge. The conclusion suggests practical implications in pre-school and school teaching.Incluida en el contexto teórico de la literacia emergente, la presente investigación llevada con setenta y cuatro jóvenes franceses revela que el conocimiento del nombre de las letras reglamenta los comportamientos de escritura precoces e influye en el aprendizaje implícito de las relaciones letra-fonema así como el desarrollo de la sensibilidad fonémica. Por proporcionar una identidad fonólogica a las letras, el nombre de las letras favorece el manejo y la conceptualización de la escritura alfabética. El conocimiento del nombre de las letras se revela una adquisición crítica, conclusión que sugiere implicaciones prácticas para la enseñanza preescolar y escolar.Im theoretischen Kontext der Literacy bei kleinen Kindern macht vorliegende bei 74 jungen Franzosen geführte Forschungsarbeit bekannt, dass die Kenntnis der Buchstabennamen das Schreibverhalten beim Frühschreiben bestimmt und das implizite Lernen der Buchstaben-Phonem-Verbindungen beeinflusst so wie die Entwicklung der phonemischen Empfindlichkeit. Da er den Buchstaben eine phonologische Identität verleiht, fördert der Buchstabenname die Bedienung und Konzeptualisierung des alphabetischen Schreibens. Die Kenntnis der Buchstabennamen erweist sich als ausschlaggebende Erwerbung. Dieses Shlusswort bietet praktische Folgen im vorschulischen und schulischen Unterrichten an

Sub-surface Oxygen and Surface Oxide Formation at Ag(111): A Density-functional Theory Investigation

To help provide insight into the remarkable catalytic behavior of the oxygen/silver system for heterogeneous oxidation reactions, purely sub-surface oxygen, and structures involving both on-surface and sub-surface oxygen, as well as oxide-like structures at the Ag(111) surface have been studied for a wide range of coverages and adsorption sites using density-functional theory. Adsorption on the surface in fcc sites is energetically favorable for low coverages, while for higher coverage a thin surface-oxide structure is energetically favorable. This structure has been proposed to correspond to the experimentally observed (4x4) phase. With increasing O concentrations, thicker oxide-like structures resembling compressed Ag2O(111) surfaces are energetically favored. Due to the relatively low thermal stability of these structures, and the very low sticking probability of O2 at Ag(111), their formation and observation may require the use of atomic oxygen (or ozone, O3) and low temperatures. We also investigate diffusion of O into the sub-surface region at low coverage (0.11 ML), and the effect of surface Ag vacancies in the adsorption of atomic oxygen and ozone-like species. The present studies, together with our earlier investigations of on-surface and surface-substitutional adsorption, provide a comprehensive picture of the behavior and chemical nature of the interaction of oxygen and Ag(111), as well as of the initial stages of oxide formation.Comment: 17 pages including 14 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Insights into the function of silver as an oxidation catalyst by ab initio, atomistic thermodynamics

To help understand the high activity of silver as an oxidation catalyst, e.g., for the oxidation of ethylene to epoxide and the dehydrogenation of methanol to formaldehyde, the interaction and stability of oxygen species at the Ag(111) surface has been studied for a wide range of coverages. Through calculation of the free energy, as obtained from density-functional theory and taking into account the temperature and pressure via the oxygen chemical potential, we obtain the phase diagram of O/Ag(111). Our results reveal that a thin surface-oxide structure is most stable for the temperature and pressure range of ethylene epoxidation and we propose it (and possibly other similar structures) contains the species actuating the catalysis. For higher temperatures, low coverages of chemisorbed oxygen are most stable, which could also play a role in oxidation reactions. For temperatures greater than about 775 K there are no stable oxygen species, except for the possibility of O atoms adsorbed at under-coordinated surface sites Our calculations rule out thicker oxide-like structures, as well as bulk dissolved oxygen and molecular ozone-like species, as playing a role in the oxidation reactions.Comment: 15 pages including 9 figures, Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Effect of Lactobacillus rhamnosus CGMCC1.3724 supplementation on weight loss and maintenance in obese men and women

The present study investigated the impact of a Lactobacillus rhamnosus CGMCC1.3724 (LPR) supplementation on weight loss and maintenance in obese men and women over 24 weeks. In a double-blind, placebo-controlled, randomised trial, each subject consumed two capsules per d of either a placebo or a LPR formulation (1·6×108 colony-forming units of LPR/capsule with oligofructose and inulin). Each group was submitted to moderate energy restriction for the first 12 weeks followed by 12 weeks of weight maintenance. Body weight and composition were measured at baseline, at week 12 and at week 24. The intention-to-treat analysis showed that after the first 12 weeks and after 24 weeks, mean weight loss was not significantly different between the LPR and placebo groups when all the subjects were considered. However, a significant treatment×sex interaction was observed. The mean weight loss in women in the LPR group was significantly higher than that in women in the placebo group (P=0·02) after the first 12 weeks, whereas it was similar in men in the two groups (P=0·53). Women in the LPR group continued to lose body weight and fat mass during the weight-maintenance period, whereas opposite changes were observed in the placebo group. Changes in body weight and fat mass during the weight-maintenance period were similar in men in both the groups. LPR-induced weight loss in women was associated not only with significant reductions in fat mass and circulating leptin concentrations but also with the relative abundance of bacteria of the Lachnospiraceae family in faeces. The present study shows that the Lactobacillus rhamnosus CGMCC1.3724 formulation helps obese women to achieve sustainable weight los

Classroom teaching versus blended learning: lessons learnt from the comparison

International audienceOn-line learning drawing upon new technologies is often presented as the future of education. This article compares, from teachers’ point of view, two Master programs delivering the same degree. One is based upon classroom teaching and face to face seminars, the other one relies on blended learning. Lessons learnt from the comparison are threefold. First, teaching simultaneously in both systems enabled cross-fertilization and enrichment of teaching methods. Second, a strong relational network, between teachers and trainees and among trainees, proved to be key success factor in the distance learning system. Third, the high quality of the blended learning program reflected in the excellent rate of success required a great deal of resources and is eventually much more expensive than the classroom training program