Chemical species

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Development of numerical methods for the reactive transport of chemical species in a porous media : a nonlinear conjugate gradient method

Development of numerical methods for the reactive transport of chemical species in a porous media : a nonlinear conjugate gradient method

archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de transport of chemical species in a porous media : a

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Bioaccessibility of selenium after human ingestion in relation to its chemical species and compartmentalization in maize

Bioaccessibility of selenium after human ingestion in relation to its chemical species and compartmentalization in maize

Maryse Castrec-Rouelle Abstract Selenium is a micronutrient needed by all living organisms including humans, but often present in low concentration in food with possible deficiency. From another side, at higher concentrations in soils as observed in seleniferous regions of the world, and in function of its chemical species, Se can also induce (eco)toxicity. Root Se uptake was therefore studied in function of its initial form for maize (Zea mays L.), a plant widely cultivated for human and animal food over the world. Se phytotoxicity and compartmental- ization were studied in different aerial plant tissues. For the first time, Se oral human bioaccessibility after ingestion was assessed for the main Se species (Se IV and Se VI ) with the BARGE ex vivo test in maize seeds (consumed by humans), and in stems and leaves
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Technical note: Implementation of prescribed (OFFLEM), calculated (ONLEM), and pseudo-emissions (TNUDGE) of chemical species in the Modular Earth Submodel System (MESSy)

Technical note: Implementation of prescribed (OFFLEM), calculated (ONLEM), and pseudo-emissions (TNUDGE) of chemical species in the Modular Earth Submodel System (MESSy)

od : DATA Fig. 2. Data flow between the MESSy submodels OFFLEM, ON- LEM, and TNUDGE within the overall MESSy framework. Boxes with color gradation show the generic (infrastructure) MESSy sub- models, i.e., the data import interface (NCREGRID), the memory management interface (data transfer/export interface, DATA), and the tracer interface for chemical species (TRACER). BML denotes the MESSy base model layer, e.g., a general circulation model (GCM). Numbers in rhombs indicate the emission method, as ex- plained in the text. The emission type is denoted as 2-D (surface), Nx2D (multilayer), and 3-D (volume). Note that ONLEM uses data from the base model (delivered via DATA) to calculate the emis- sions.
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Measurement of Fission Products and Chemical Species released by Experimental Samples irradiated in the Jules Horowitz Reactor

Measurement of Fission Products and Chemical Species released by Experimental Samples irradiated in the Jules Horowitz Reactor

3 A second category of instrumentation is directly connected to the sample. A lot of physical or chemical parameters can be monitored, on-line when it is technically feasible. Instrumentation can be either fixed on a sample component (clad temperature, elongation or strain, crack initiation and propagation on a specimen…) or introduced in the sample (central fuel temperature, fuel elongation) or in relation with the sample inner free volume (gas total pressure, differential pressure…). In practice nuclear instrumentation in MTRs (for in-core locations or for experiments in core or in reflector), or more generally in harsh and closed environments imposed by in-reactor nuclear measurements (fission or fusion), constitutes a specific innovation and development domain, with a lot of remarkable progresses in the recent years. This paper doesn’t describe instrumentation physical principle and technology, which are topics of numerous other papers. Only a few recent review papers are mentioned here in ref. [3], [4], [5], [6].The domain is in continuous progress. In particular measurement methods without contact (e.g. by optic fibre [7] or ultrasonic waves [8]) are capable to provide new information under neutron flux.
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Sensitivity of chemical species to climatic changes in the last 45 kyr as revealed by high-resolution Dome C (East Antarctica) ice-core analysis

Sensitivity of chemical species to climatic changes in the last 45 kyr as revealed by high-resolution Dome C (East Antarctica) ice-core analysis

F ðng cm 2 a 1 Þ ¼ Cðng cm 3 Þ  Aðcm w:e: a 1 Þ Both the use of concentration and the use of flux to study the temporal profiles of climatic and environmental markers along an ice core have advantages and disadvantages. Concentration is an independent chemical measurement and thus more reliable, but changes in concentration are dependent on variation in source intensity and transport efficiency as well as in accumulation rate, especially for sites where dry deposition is important or dominant (low- accumulation-rate areas, such as Dome C: Legrand, 1987). Flux (net deposition mass) is calculated by multiplying concentration by accumulation rate and is potentially affected by larger errors, mainly related to the reliable reconstruction of past accumulation rate from the isotopic profile. On the other hand, flux is virtually independent of accumulation rate at Dome C, dominated by dry-deposition processes, and therefore more suitable for assessing changes in atmospheric load. We use both parameters, preferring fluxes when studying the effects of source and transport changes, and concentrations when describing the compre- hensive sensitivity (driven by accumulation rate, source and transport changes) of chemical profiles to climate variations.
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Identification of chemical species created during γ‐irradiation of antioxidant used in polyethylene and polyethylene‐ co ‐vinyl acetate multilayer film

Identification of chemical species created during γ‐irradiation of antioxidant used in polyethylene and polyethylene‐ co ‐vinyl acetate multilayer film

The purpose of this article is to highlight the degradation products we may expect from the radiative degradation of primary and secondary antioxidants and to address the complexity of the proper identification of the by-products thereof. A comprehensive profile of prone-to-migrate by- products of the four antioxidants is thus established by analytical means and by degradation pathways. The degra- dation pathways reveal that numerous alkyl radicals are created, leading to the generation of numerous intermedi- ates. Even though we were not able to detect the ESR sig- nal of these radicals, the degradation pathways emphasize a possible radical reaction leading to the creation on the film surface of radicals which can then potentially gener- ate hydro(gen) peroxides. This article summarizes proba- ble degradation mechanisms of γ-irradiated antioxidants as key events to better apprehend the reactivity and the lifetime of intermediate radical species. We propose an
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Technical note: The MESSy-submodel AIRSEA calculating the air-sea exchange of chemical species

Technical note: The MESSy-submodel AIRSEA calculating the air-sea exchange of chemical species

10 tional requirements can be expected to improve the ability of global models to predict the chemical composition of the atmosphere. This is especially required for the inter- pretation of observational data, notably for data obtained on ships. Currently, the major limitation of this approach is, however, a good characterisation of the water concentra- tion of the tracers. Additional measurements are needed to improve our knowledge in

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Physico-chemical approach of polymer chemical ageing: a short review

Physico-chemical approach of polymer chemical ageing: a short review

Manuscript received 13th October 2020, accepted 19th November 2020. 1. Introduction Polymers and composites become increasingly used because weight and costs saving but also improved specific mechanical properties such as ratio of stiffness or failure stress over density or fatigue resistance. For many industrial applications, long lasting properties are needed which arises the issue of interaction between polymer and its environment. One can usually distinguish • physical ageing where the polymer skeleton remains unchanged but the distance be- tween polymer chains is modified for example in case of water diffusion in an epoxy- diamine thermoset networks [1, 2], or physical ageing by structural relaxation for glassy polymers aged under their glass transition temperature [3]. Diffusion of penetrants gen- erally induces a decrease in glass transition and stiffness [1, 4, 5], contrarily to structural relaxation inducing an increase in yield stress for example [6, 7]. Physical ageing is in principle reversible [8]. In the case of water ageing, the amount of desorbed water after complete drying must correspond to amount of absorbed one during immersion (apart if penetrant reacts which is a case of chemical ageing described here below [9]).
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Delineation of Taxonomic Species within Complex of Species: Aeromonas media and Related Species as a Test Case

Delineation of Taxonomic Species within Complex of Species: Aeromonas media and Related Species as a Test Case

Insights about speciation processes in a population can also be provided by MLP and genomics. The chaperone protein DnaJ participates actively to the response to hyperosmotic and/or heat shocks in a DnaK-independent pathway ( Caplan et al., 1993 ). Among the Media SC population (41 isolates), a 3-amino acid deletion in the sequence of protein DnaJ was detected in 95% (n = 20) of the strains belonging to A. rivipollensis and in 17% (n = 3) to A. media, while absent from all the strains belonging to other species of the genus. Genomics data from 14 genomes showed that 3 genes presumed to be associated to the osmotic stress response were specific to A. rivipollensis genome that potentially acquired them by HGT from Betaproteobacteria. Although the absence of homologs does not mean that the function is absent in A. media, one scenario suggested by these results is that the type of response to hyperosmotic stress in particular niches could be involved in the speciation of A. rivipollensis. We cannot exclude that similar role of positive selection by environmental conditions could be suspected from the annotation of the specific genome of each Media SC clades. In fact, most CDS are annotated as “hypothetical proteins” or as protein involved in adaptation to environment and environment changes such as transporters or transcriptional regulators, but this assessment requires further studies.
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Calonectria species and their Cylindrocladium anamorphs: species with clavate vesicles

Calonectria species and their Cylindrocladium anamorphs: species with clavate vesicles

culture CBS 749.70. Cultural characteristics: Cultures sterile, white. Substrate and distribution: See Crous (2002). Notes: The genus Calonectria is based upon Calonectria pyrochroa (= Ca. daldiniana), which is linked to a Cylindrocladium ilicicola anamorph (Rossman 1979, Brayford & Chapman 1987, Crous 2002). All cultures thus far collected by us, and thought to be representative of Cy. ilicicola, have turned out to represent other species, and hence no authentic cultures of Cy. ilicicola have as yet been obtained. A strain not previously studied by us was recently retrieved from the CBS collection (CBS 749.70). Although the isolate sporulated poorly, it was accompanied by a very good specimen, which proved to be identical to the original holotype collection. We therefore designate this specimen as epitype, thereby obtaining an authentic strain of Cy. ilicicola for further study.
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Species boundaries in the Himantura uarnak species complex (Myliobatiformes: Dasyatidae)

Species boundaries in the Himantura uarnak species complex (Myliobatiformes: Dasyatidae)

Fig. S1. Himantura uarnak species complex. Output diagram of Bayesian population structure analysis [S TRUCTURE : Falush et al., Mol. Ecol. Resour. 7 (2007) 574–578] when the number of parent populations is K=3. Individual probabilities of assignment are shown on the y-axis. Individuals are represented by vertical bars and sorted by mitotype (Clades I-IV). Individual ir007, of a distinct cluster according to correspondence analysis [G ENETIX : http:// www.genetix.univ-montp2.fr/ ], is marked by an asterisk. Horizontal black traits underline

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Biological and chemical assays and chemical constitution of the vitamins

Biological and chemical assays and chemical constitution of the vitamins

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Biological and chemical assays and chemical constitution of the vitamins. Wha[r]

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Anopheles species associations in Southeast Asia: indicator species and environmental influences

Anopheles species associations in Southeast Asia: indicator species and environmental influences

generate vast quantities of data on a wider scale, but sam- pling design is often not optimal for exploring biodiversity issues. This is the case of the MALVECASIA project [5], which operated a major collection effort throughout Laos, Cambodia and Vietnam capturing Anopheles between 2003 and 2005 in more than a hundred sites to monitor insecticide resistance. For logistic reasons, surveys were not concurrent. In this context studying species associa- tions and their relation to the environment offer some op- portunities. Associations are less subject to sampling error than individual species. Moreover, some species such as An. dirus s.l. are difficult to collect and abundance varies greatly according to the rain history of the previous days [6]. Occurrence of such elusive species could be revealed by the presence of associated species.
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Residues: Rethinking Chemical Environments

Residues: Rethinking Chemical Environments

chemists synthesized them. During the middle decades of the twentieth century, as the electrical infrastructure for the growing industrial economies was built, PCBs entered landscapes, workplaces, and households, in air conditioners, fluorescent light fixtures, refrigerators, television sets, and electrical transformers. Their insolubility in water and resistance to corrosion led PCBs to be used in carbonless copy paper, paints, sealants, ironing board covers, and plastic bottles. Because of their very slow degradation (physically or biologically), PCBs will linger in the environment indefinitely, though they were banned decades ago, and their fat solubility means that these toxic residues continue to bio-accumulate in food webs (Spears 2014: 1–4; US Senate, Committee on Environment and Public Works, Subcommittee on Superfund and Environmental Oversight 1988: ch. 2). Michel Serres observes that “pollution comes from measurable residues of the work and transformations related to energy, but fundamentally it emanates from our will to appropriate, our desire to conquer and expand the space of our properties” (Serres 2011: 42). Serres’ work reminds us that the irreversibility of residues emanates not only from the molecular nature of the chemical substances, but also from the politics of production and regulation––of decisions to create toxicants as well as decisions to not clean up the leftovers (Reinhardt 2010). As irreversible objects, these residues––both material and political––can’t simply be undone, undermining the idea that there is a “pre-” era to which we can return, even if politically and economically powerful actors want it so (Shotwell 2016; Tsing 2015). As Jens Beckert has argued, capitalism tends to restrict attention to future possibilities (Beckert 2016). Residues remind us that the past cannot be ignored.
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Chemical Diversity of Apatites

Chemical Diversity of Apatites

The formation of bone and enamel crystals is strictly circumvented to given domains. In addition to ionic crystal growth inhibitors, several macromolecules are involved or interfere with the crystal formation. Biological fluids are supersaturated with respect to stoichiometric hydroxyapatite. The chemical analysis of ultracentrifuged blood plasma gives an ionic product close to that of OCP [17]. This value is significantly lower than that of Simulated Body Fluids (SBF) [18] due to the existence of mineral ions bound to plasma proteins. The composition of biological fluids in the vicinity of forming enamel or forming or remodelling bone is not known, but it seems probable that there is a local control. Carbonic-anhydrase enzyme, for example, has been shown to play a role during the formation of enamel crystals. However, this does not seem sufficient to promote a spontaneous precipitation of calcium phosphates. Additional control is brought along by the existence of nucleation agents and an organic matrix able to orient crystal growth [19]. The interactions of organic molecules with apatite crystals are not known at a structural level. It can, however, be inferred that the hydrated surface layer on the crystals plays an important role.
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The chemical abstract machine

The chemical abstract machine

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Biopsy-implantable chemical sensor

Biopsy-implantable chemical sensor

The sensor presented in this thesis is designed to monitor cancer directly from within a tumor.. It measures clinically relevant markers that may indicate how the tumor i[r]

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Chemical prescription for durability

Chemical prescription for durability

A good sealer penetrates the concrete or masonry, and the dry film produces an effective barrier to water and salt infiltra- tion, which prevents buildup of dirt and deleterious matter w[r]

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Dry Chemical Extinguishing Agents

Dry Chemical Extinguishing Agents

Reagent grade sodium bicarbonate was assigned sample No.8.... Apparatus.[r]

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Autecology of broadleaved species

Autecology of broadleaved species

This diagram can be used to verify the suitability of the species to the site conditions by checking the Adishatz soil analysis values (brown dotted line in the example in fig.2), which must be higher than those given for the species to ensure optimum growth. The comparison must be done on a soil profile representative of the site being studied; the chemical analysis is performed for the A horizon containing organic matter and supplemented by an underlying horizon representative of the profile (analysis without organic matter). Samples should preferably be taken in a trench, at least for the upper horizons and possibly on several representative trench faces. Soil samples are taken from the entire height of the horizon, within limits – e.g. for a 30-90 cm horizon, take samples between 40 cm and 80 cm – and avoiding contamination of the sample from other horizons. Analysis may be performed for a group of several samples (from 4-5 places in the same horizon and the same type of soil) to obtain an average value over a homogeneous area. The samples should be sent to an approved soil analysis laboratory (for further details, see: Larrieu & Jabiol, Rev. For. Fr. LIII - 5-2001, p. 558-567).
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