L'espace vert public, lieu d'interactions entre société et biodiversité

L'EVP est un écosystème où se croisent la valeur esthétique et l'intérêt fonctionnel du végétal ; c'est également un espace d'interaction privilégié entre l'homme et la biodiversité. Cette étude cherche à lancer le débat sur l'effet des activités humaines sur la dynamique végétale dans les EVP, d'une part. Elle a tenté d'explorer la relation entre les pratiques, les représentations et l'image du sauvage, incarné par la diversité biologique urbaine, d'autre part. L'étude de la richesse, de la diversité et de la similarité de la flore urbaine a confirmé non seulement l'effet perturbateur des pratiques sur la composition floristique des pelouses urbaines, mais elle a également corroboré l'idée de l'existence d'un gradient de perturbation, de part et d'autre des chemins de fréquentation dans les pelouses. Par ailleurs l'analyse des pratiques et des représentations des usagers, qui relient l'individu au végétal, a contribué à mettre en lumière la question des usages des EVP en relation au gradient urbain. Elle a aussi confirmé l'importance attribuée par les usagers à la présence de l'espace sauvage dans les EVP (68 % des interrogés le préfèrent à l'espace jardiné). La prise en compte des interactions entre usagers et dynamiques floristiques ne devrait plus être ignorée 14/17 dans la conception et surtout dans la gestion des EVP. Ces interactions constituent un champ de recherche qui attend toujours la mobilisation d'une communauté scientifique (écologues, géographes, sociologues, urbanistes, etc.) dotée d'une vision pluridisciplinaire (Clergeau, 2007 ; Bagouet et Clergeau, 2008)

The first-time phenomenon: successful students' mathematical crisis in secondary-tertiary transition

The huge difficulties related to the transition from secondary to tertiary mathematics are documented by several official data. The analysis of these difficulties is a main issue in educational research at undergraduate level. It is of particular interest the case of the students who choose mathematics as a major. In fact, for the most part, they are students considered excellent in mathematics during secondary school, they seem to have the cognitive resources to succeed, but, in many cases, they encounter several difficulties during their university experience. Therefore, it appears particularly interesting to study also the affective sources and consequences of these difficulties. With this aim, we developed a qualitative and narrative study focused on students’ reflec- tions about their mathematical difficulties in the university experience

The role of affect in failure in mathematics at the university level: the tertiary crisis

The tertiary transition between secondary school and university appears to be an insurmountable struggle for many students. This is also the case, surprisingly, in a certain sense, of students enrolled in Mathematics degree courses, and therefore students considered “gifted” with respect to mathematics. This case seems particularly interesting from an affective point of view: these students often live failure in mathematics as a tragedy, and – above all – initially they are not able to interpret their failure. For these reasons, it appears crucial to investigate which role is played by emotions in the emergence and management of this crisis, and how the students’ view of mathematics and their self-perception develop in the tertiary crisis period

Hydrogen photo-production by mixotrophic cultivation of chlamydomonas reinhardtii: Interaction between organic carbon and nitrogen

Hydrogen photo-production by a wild type and two engineered strains of Chlamydomonas reinhardtii was investigated. Growth rate values and hydrogen yields attained as the concentration of acetate and nitrogen vary were compared. In the analysis of microalgal growth, the interaction between organic carbon (acetate) and nitrogen (nitrate) was investigated by recourse to an experimental factorial design. This analysis evidenced the existence of a statistically significant interaction between organic carbon and nitrate. Hydrogen production was attained by cultivating microalgae previously grown in mixotrophic regime with sulphur deprived medium. The influence of varying the photobioreactor headspace on hydrogen production was investigated. This analysis revealed an increase in the hydrogen produced per unit volume of culture of about one order of magnitude when the headspace volume is modified from 100 to 350 mL. This result provides valuable indications on how to design and operate photobioreactors for hydrogen production optimization and was thoroughly discussed in terms of the metabolic pathways activated by sulphur depletion. ©2014, AIDIC Servizi S.r.l

Lanthanum biosorption by different Saccharomyces cerevisiae strains

Biosorption can be a promising technology in rare earth metal separation and recovery due to the low costs of waste biomasses (used as biosorbents) and the high selectivity exploiting specific interaction between metals and biological active sites. In this work, Saccharomyces cerevisiae biomass was used to recover lanthanum. Biosorption properties of two S. cerevisiae strains, wild type and rim20. mutant, have been tested. Potentiometric titrations were carried out for rim20. mutant strain and compared with wild type. Nature of the main active sites and their concentration were determined by implementing mechanistic models. Carboxylic, amino and phosphoric sites are the main groups present. Higher concentration of negatively charged sites was found in rim20. (0.0024 mol/g) than in wild type (0.0022 mol/g). The rate of lanthanum biosorption process is very fast requiring only 10-20 minutes to reach equilibrium condition for both strains. Then biosorption equilibrium tests were done for both biomasses by testing two equilibrium pH (4.0 and 6.0). Maximum uptake capacities (qmax) were: 70 mg/g and 40 mg/g at pH 4.0 for rim20. and wild type, respectively, and 67 mg/g and 80 mg/g at pH 6.0 for wild type and rim20., respectively. These data evidenced that: rim20. mutant had a higher maximum biosorption capacity with respect to wild type counterpart, and that pH had a relevant effect on lanthanum removal. S. cerevisiae yeast denoted good lanthanum biosorption properties and, between tested strains, rim20. was found to be the most promising for such aim

The Secondary-Tertiary Transition in Mathematics. Successful Students in Crisis

The transition from secondary school into university mathematics – also referred to as secondary-tertiary transition (STT) – is a sensitive moment for many students, also for those who have achieved high marks at the end of their schooling and are considered excellent in mathematics in the school context. The cognitive aspect has interested researchers since the late seventies, but the interest in other two aspects (social and emotional aspects) is growing. Recently we have investigated the emotional aspect further and we will report here on some of our findings underlying the necessary developments

Two stage process of microalgae cultivation for starch and carotenoid production

Biotechnological processes based on microalgae cultivation are promising for several industrial applications. Microalgae are photoautotrophic microorganisms and can thus grow by using renewable and inexpensive resources as sunlight, inorganic salts, water and CO2. They can store high amounts of neutral lipids (bioil), carbohydrates (mainly starch), carotenoids (such as lutein, astaxanthin, beta-carotene), proteins and other molecules. Productions of lipids and carbohydrates have recently received an increasing interest for biofuel production, while proteins, carotenoids and other minor products are usable as feed additives and nutraceutical compounds. Biofuel production from microalgae is not yet economically sustainable, while there are different industrial plants in the world for the production of high values chemicals as carotenoids. Starch production from microalgae has been investigated mainly for the production of biofuels (e.g. bioethanol) by successive fermentation. However, purified starch can be used for other aims such as the production of bioplastics. Superior plants as corn, potato and wheat are currently used for this purpose. However, there are different environmental and economic issues related to the use of fertile lands and edible plants for these kinds of productions. Microalgae can solve these social and ethical issues because they can grow on nonfertile lands and also reach starch productivity per hectare higher than plants. In this work, the production of starch and carotenoids from Scenedesmus sp. microalgal strain is reported. A two-stage process has been developed in order to reduce operative and investment costs. In the first stage, microalgae are cultivated in photoautotrophic conditions and then, when biomass concentration rises and light becomes a limiting factor for growth, microalgae are transferred to a heterotrophic reactor. In this reactor, microalgae are cultivated by using wastewaters as source of nutrients (mainly organic carbon). Microalgae use organic carbon to synthesize starch and simultaneously reduce the content of pollutants in the wastewater (codepuration). Biomass separated by the culture medium is treated for the extraction of lipids containing different antioxidant carotenoids (such as astaxanthin and lutein) and starch granules as raw material for biopolymers

Fully discrete polynomial de Rham sequences of arbitrary degree on polygons and polyhedra

In this work, merging ideas from compatible discretisations and polyhedral methods, we construct novel fully discrete polynomial de Rham sequences of arbitrary degree on polygons and polyhedra. The spaces and operators that appear in these sequences are directly amenable to computer implementation. Besides proving exactness, we show that the usual sequence of Finite Element spaces forms, through appropriate interpolation operators, a commutative diagram with our sequence, which ensures suitable approximation properties. A discussion on reconstructions of potentials and discrete $L^2$-products completes the exposition