356 research outputs found
A Kinetic Study of the Gas-Phase O( 1 D) + CH3OH and O( 1 D) + CH3CN Reactions. Low Temperature Rate Constants and Atomic Hydrogen Product Yields
No full textInternational audienceAtomic oxygen in its first excited singlet state, O(1 D), is an important species in the photochemistry of several planetary atmospheres and has been predicted to be a potentially important reactive species on interstellar ices. Here, we report the results of a kinetic study of the reactions of O(1 D) with methanol, CH3OH, and acetonitrile, CH3CN, over the 50-296 K temperature range. A continuous supersonic flow reactor was used to attain these low temperatures coupled with pulsed laser photolysis and pulsed laser induced fluorescence to generate and monitor O(1 D) atoms respectively. Secondary experiments examining the atomic hydrogen product channels of these reactions were also performed, through laser induced fluorescence measurements of H(2 S) atom formation. On the kinetics side, the rate constants for these reactions were seen to be large (> 2 ´ 10-10 cm 3 s-1) and consistent with barrierless reactions, although they display contrasting dependences as a function of temperature. On the product formation side, both reactions are seen to yield non-negligible quantities of atomic hydrogen. For the O(1 D) + CH3OH reaction, the derived yields are in good agreement with the conclusions of previous experimental and theoretical work. For the O(1 D) + CH3CN reaction, whose H-atom formation channels had not previously been investigated, electronic structure calculations of several new product formation channels were performed to explain the observed H-atom yields. These calculations demonstrate the barrierless and exothermic nature of the relevant exit channels, confirming that atomic hydrogen is also an important product of the O(1 D) + CH3CN reaction
Corporate Social Responsibility before CSR Practices at the Company Aluminium du Cameroun, 1950s-1970s.
No full textCorporate social responsibility (CSR) is a relatively recent phenomenon for companies and their stakeholders. However, we cannot ignore its historical roots. Many companies, especially in industry, developed social and environmental policies and practices a long time ago. These practical and historical dimensions still remain absent from the academic literature on CSR. In this paper, we set out to study a case over an extended period—from 1950s until 1970s—in order to understand how manufacturers took into account the various economic, social and environmental aspects of their activity, when they made an investment and subsequently ran an aluminium production site. The case of the company Alucam, implanted in Cameroon, shows how manufacturers integrated the Triple Bottom Line well before the ‘invention’ of CSR. Since i ts creation in 1957, this plant designed to produce primary aluminium has systematically applied a policy that simultaneously integrated the economic, environmental and social impacts of its activity. However, such visible permanency masks important changes in the way that CSR has been applied over time. This case study provides a better understanding of the process of building CSR in the aluminium industry. With that goal in mind, our methodology is historical. Research was mainly carried out by means of studying the Alucam archives. Such empirical research, highlighting the reality of the practices implemented in companies, constitutes an original contribution to the history of CSR.responsabilité sociale des entreprises; case study; history; environment; development; paternalism; Corporate Social Responsibility;
Nabokov et la censure
No full textThis article sheds light on the tension between art and politics in Nabokov’s career. Before he became an American author, Nabokov was subjected to political censorship in his motherland, with a complete disregard of and lack of interest in the literary qualities of his novels. Then, the article studies how Lolita was banned in different countries, be it in France or elsewhere in the world. The reason for this ban was not aesthetics but ethics. In many respects, the censorship Lolita suffered from is an illustration of the difficulties that great authors such as Nabokov, James Joyce, D. H. Lawrence or Henry Miller were subjected to when it came to publishing their novels in the 20th century. Nabokov’s letters and exclusive archives from Gallimard will show some of the judicial mishaps / streaks of bad luck that Nabokov’s novel met with. In the end, literary quality was made part of judicial decisions and it is thanks to its aesthetic value that censorship on Lolita was finally lifted
Analysis Of The Ch<sub>2</sub>oh Radical Spectrum With An Iam Tunneling Approach
No full text"Early {\em ab initio} calculations\footnote{Saeb\o, Radom, and
Schaefer, {\em J.\ Chem.\ Phys.}~{\bf 78} (1983) 845; Marenich
and Boggs, {\em J.\ Chem.\ Phys.}~{\bf 119} (2003) 3098; and
Ibid., {\em J.\ Chem.\ Phys.}~{\bf 119} (2003) 10105} revealed
that the hydroxymethyl radical (\ce{CH2OH}) is a non-rigid
species exhibiting a complicated potential energy surface. It
displays 4 non-superimposable, energetically equivalent,
equilibrium configurations and 4 maxima, approximately
300 and 1500\,cm above the equilibrium configurations.
The large amplitude motion of the radical can be pictured as
an internal rotation of the \ce{CH2} group with respect to the
\ce{OH} group. The axis of internal rotation is the \ce{CO} bond
and the two-fold symmetry hindering potential is characterized
by a barrier height of 1500\,cm. Aided by new {\em ab
initio} results, the torsional levels associated with this
torsional motion were computed. The energy levels display a
tunneling splitting which, for the ground torsional level,
was found to be smaller than 0.1~cm.
As the large amplitude motion of the hydroxymethyl radical
seems to be well described by the high barrier approximation,
the tunneling IAM water dimer formalism\footnote{Hougen,
{\em J.\ Mol.\ Spectrosc.}~{\bf 114} (1985) 395; and Coudert and
Hougen, {\em J.\ Mol.\ Spectrosc.}~{\bf 130} (1988) 86} was
used to derive a fitting approach aimed at accounting for its rotation-tunneling energy. The effects of the fine spin-rotation and hyperfine spin-spin couplings were also included since there is an unpaired electron.
In the paper, the analysis with the IAM approach of already available\footnotetext[3]{Bermudez, Bailleux, and Cernicharo, {\em A\&A}~{\bf 598} (2017) A9}\footnotetext[4]{Chitarra, Martin-Drumel, Gans, Loison, Spezzano, Lattanzi, M\""uller, and Pirali, {\em A\&A}~{\bf 644} (2020) A123} and newly measured sub-millimeter wave spectroscopic data will be reported. The fitted value of the tunneling splitting
will be compared to that retrieved from the torsional energy
level calculation. The rotational dependence of the tunneling
splitting will be discussed."Made available in DSpace on 2021-09-24T21:09:18Z (GMT). No. of bitstreams: 2
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L’unità incrinata. Heisenberg tra Goethe, pensiero greco e Weltformel
No full textLe scienze nascono dalla filosofia, dalla quale trovano autonomia epistemologica man mano che definiscono i loro ambiti, i loro metodi e i loro linguaggi. Il terreno comune sul quale si dispiegano sia la scienza sia la filosofia è quello della storia. Solo chiarendo e ricostruendo sul piano storico i rapporti tra scienza, filosofia e contesto culturale e sociale è possibile comprendere in modo approfondito autori, teorie e correnti di pensiero. La prospettiva storica interagisce inoltre con la consapevolezza teorica della scienza e della filosofia e può essere considerata parte integrante della riflessione di queste discipline.
Silvia Caianiello, Dario Generali, Fabio Minazzi (a cura di).
Contributi di: Ugo Baldini, Maria Teresa Costa, Stefano Furlan, Rocco Gaudenzi, Laurent Loison, Cesare Maffioli, Roberto Marcuccio, Renato G. Mazzolini, Pietro Daniel Omodeo, Barbara Orland e Hans-Jörg Rheinberge
Bifidobacterium animalis MSMC83 Improves Oxidative Stress and Gut Microbiota in D-Galactose-Induced Rats
No full textThe development of many chronic diseases is associated with an excess of free radicals leading to harmful oxidative stress. Certain probiotic strains have been shown to have antioxidant and anti-aging properties and are an important resource for development of microbial antioxidants. The present study aimed to explore the protection offered by Bifidobacterium animalis strain MSMC83 in a model of oxidative stress induced by D-galactose (D-gal). Male Sprague Dawley rats were randomly allocated to four groups: a control group injected with saline, a group injected subcutaneously with D-galactose, a probiotic group injected with D-galactose and administered B. animalis MSMC83 (109 CFU/mL) via daily oral gavage, and an ascorbic acid group. The probiotics significantly increased the superoxide dismutase, catalase, and glutathione peroxidase and significantly decreased the malondialdehyde in the plasma and livers of D-galactose-treated rats. Moreover, tumor necrosis factor-alpha level in the liver was significantly decreased. Furthermore, the treatment with B. animalis MSMC83 restored the microbiota diversity after D-galactose injection. Therefore, our results supported a beneficial role of B. animalis MSMC83 in alleviating oxidative stress through the increased expression of antioxidant enzymes and reduction of pro-inflammatory cytokines in rats. Our study suggests that B. animalis MSMC83 may be part of a healthy diet to prevent oxidative stress-associated diseases
Le cosmopolitisme linguistique de Vladimir Nabokov
No full textNabokov was first a Russian author before he switched to writing his novels in English at the beginning of the 1940s. His multilingualism left a significant imprint on his prose in the form of code-switching (i. e. the presence of foreign words in a given language). According to sociologist Vinay Dharwadker, code-switching is the linguistic manifestation of cosmopolitanism; conversely, creolization, in the sense given by Edouard Glissant, manifests itself in hybridization. First, it is important to take stock of the degree to which Nabokov’s cosmopolitanism was personal before becoming part of his aesthetic. But, in his œuvre, foreign words are far from being mere traces of his personal multilingualism: indeed, in his American novels, code-switching serves a functional role. The article ends with an analysis of one of the few cases where Nabokov resorts to hybridization, which is the literary counterpoint to his linguistic cosmopolitanism
A kinetic study of the N( 2 D) + C 2 H 4 reaction at low temperature
No full textElectronically excited nitrogen atoms N(2 D) are important species in the photochemistry of N2 based planetary atmospheres such as Titan. Despite this, few N(2 D) reactions have been studied over the appropriate low temperature range. During the present work, rate constants were measured for the N(2 D) + ethene (C2H4) reaction using a supersonic flow reactor at temperatures between 50 K and 296 K. Here, a chemical reaction was used to generate N(2 D) atoms, which were detected directly by laser induced fluorescence in the vacuum ultraviolet wavelength region. The measured rate constants displayed very little variation as a function of temperature, with substantially larger values than those obtained in previous work. Indeed, considering an average temperature of 170 K for the atmosphere of Titan leads to a rate constant that is almost seven times larger than the currently recommended value. In parallel, electronic structure calculations were performed to provide insight into the reactive process. While earlier theoretical work at a lower level predicted the presence of a barrier for the N(2 D) + C2H4 reaction, the present calculations demonstrate that two of the five doublet potential energy surfaces correlating with reagents are likely to be attractive, presenting no barriers for the perpendicular approach of the N atom to the C=C bond of ethene. The measured rate constants and new product channels taken from recent dynamical investigations of this process are included in a 1D coupled ion-neutral model of Titan's atmosphere. These simulations indicate that the modeled abundances of numerous nitrogen bearing compounds are noticeably affected by these changes.Développement d'un nouvel instrument pour l'application de la spectroscopie submillimétrique à l'étude de la réactivité pour l'astrochimi
Phase transitions in generalized chiral or Stiefel's models
No full textPACS. 05.50.+q Lattice theory and statistics (Ising, Potts, etc.) - 75.10.Hk Classical spin models - 05.70.Fh Phase transitions: general studies,
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