Showing papers by "Paul Sabatier University published in 2005"
TL;DR: A critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ≥ 5 cm diameter, directly harvested in 27 study sites across the tropics, is provided.
Abstract: Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contri- bution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regres- sion models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ‡ 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional rela- tionships between aboveground biomass and the prod- uct of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regres- sion model involving wood density and stem diameter only. Our models were tested for secondary and old- growth forests, for dry, moist and wet forests, for low- land and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5-6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprece- dented dataset, these models should improve the quality
2,786 citations
TL;DR: The BOLSIG+ solver as mentioned in this paper provides steady-state solutions of the BE for electrons in a uniform electric field, using the classical two-term expansion, and is able to account for different growth models, quasi-stationary and oscillating fields, electron-neutral collisions and electron-electron collisions.
Abstract: Fluid models of gas discharges require the input of transport coefficients and rate coefficients that depend on the electron energy distribution function. Such coefficients are usually calculated from collision cross-section data by solving the electron Boltzmann equation (BE). In this paper we present a new user-friendly BE solver developed especially for this purpose, freely available under the name BOLSIG+, which is more general and easier to use than most other BE solvers available. The solver provides steady-state solutions of the BE for electrons in a uniform electric field, using the classical two-term expansion, and is able to account for different growth models, quasi-stationary and oscillating fields, electron–neutral collisions and electron–electron collisions. We show that for the approximations we use, the BE takes the form of a convection-diffusion continuity-equation with a non-local source term in energy space. To solve this equation we use an exponential scheme commonly used for convection-diffusion problems. The calculated electron transport coefficients and rate coefficients are defined so as to ensure maximum consistency with the fluid equations. We discuss how these coefficients are best used in fluid models and illustrate the influence of some essential parameters and approximations.
2,633 citations
TL;DR: Apelin is identified as a novel adipocyte endocrine secretion and its potential link with obesity-associated variations of insulin sensitivity status is focused on and evidence that insulin exerts a direct control on apelin gene expression in adipocytes is provided.
Abstract: The results presented herein demonstrate that apelin is expressed and secreted by both human and mouse adipocytes. Apelin mRNA levels in isolated adipocytes are close to other cell types present in white adipose tissue or other organs known to express apelin such as kidney, heart, and to a lesser extent brown adipose tissue. Apelin expression is increased during adipocyte differentiation stage. A comparison of four different models of obesity in mice showed a large increase in both apelin expression in fat cells and apelin plasma levels in all the hyperinsulinemia-associated obesities and clearly demonstrated that obesity or high-fat feeding are not the main determinants of the rise of apelin expression. The lack of insulin in streptozotocin-treated mice is associated with a decreased expression of apelin in adipocytes. Furthermore, apelin expression in fat cells is strongly inhibited by fasting and recovered after refeeding, in a similar way to insulin. A direct regulation of apelin expression by insulin is observed in both human and mouse adipocytes and clearly associated with the stimulation of phosphatidylinositol 3-kinase, protein kinase C, and MAPK. These data provide evidence that insulin exerts a direct control on apelin gene expression in adipocytes. In obese patients, both plasma apelin and insulin levels were significantly higher, suggesting that the regulation of apelin by insulin could influence blood concentrations of apelin. The present work identifies apelin as a novel adipocyte endocrine secretion and focuses on its potential link with obesity-associated variations of insulin sensitivity status.
800 citations
TL;DR: Metal concentrations in the crops and soils were analyzed to evaluate the long-term effects of the spilled waste on the soil and the potential human exposure through food chains and showed that the physical-chemical properties of the soils obviously changed due to the different farming styles used by each individual farmer.
593 citations
TL;DR: This work used a high-throughput yeast two-hybrid (Y2H)-based technology to screen 102 bait proteins from Drosophila melanogaster, most of them orthologous to human cancer-related and/or signaling proteins, against high-complexity fly cDNA libraries.
Abstract: The Drosophila (fruit fly) model system has been instrumental in our current understanding of human biology, development, and diseases. Here, we used a high-throughput yeast two-hybrid (Y2H)-based technology to screen 102 bait proteins from Drosophila melanogaster, most of them orthologous to human cancer-related and/or signaling proteins, against high-complexity fly cDNA libraries. More than 2300 protein-protein interactions (PPI) were identified, of which 710 are of high confidence. The computation of a reliability score for each protein-protein interaction and the systematic identification of the interacting domain combined with a prediction of structural/functional motifs allow the elaboration of known complexes and the identification of new ones. The full data set can be visualized using a graphical Web interface, the PIMRider (http://pim.hybrigenics.com), and is also accessible in the PSI standard Molecular Interaction data format. Our fly Protein Interaction Map (PIM) is surprisingly different from the one recently proposed by Giot et al. with little overlap between the two data sets. Analysis of the differences in data sets and methods suggests alternative strategies to enhance the accuracy and comprehensiveness of the post-genomic generation of broad-scale protein interaction maps.
561 citations
TL;DR: Interestingly, this first large-scale comparative assessment of the antimicrobial effects of oxylipins reveals that regulators of plant defense responses are also the most active oxylippins against eukaryotic microorganisms, suggesting that such oxylIPins might contribute to plant defense through their effects both on the plant and on pathogens, possibly through related mechanisms.
Abstract: Plant oxylipins are a large family of metabolites derived from polyunsaturated fatty acids. The characterization of mutants or transgenic plants affected in the biosynthesis or perception of oxylipins has recently emphasized the role of the so-called oxylipin pathway in plant defense against pests and pathogens. In this context, presumed functions of oxylipins include direct antimicrobial effect, stimulation of plant defense gene expression, and regulation of plant cell death. However, the precise contribution of individual oxylipins to plant defense remains essentially unknown. To get a better insight into the biological activities of oxylipins, in vitro growth inhibition assays were used to investigate the direct antimicrobial activities of 43 natural oxylipins against a set of 13 plant pathogenic microorganisms including bacteria, oomycetes, and fungi. This study showed unequivocally that most oxylipins are able to impair growth of some plant microbial pathogens, with only two out of 43 oxylipins being completely inactive against all the tested organisms, and 26 oxylipins showing inhibitory activity toward at least three different microbes. Six oxylipins strongly inhibited mycelial growth and spore germination of eukaryotic microbes, including compounds that had not previously been ascribed an antimicrobial activity, such as 13-keto-9(Z),11(E),15(Z)-octadecatrienoic acid and 12-oxo-10,15(Z)-phytodienoic acid. Interestingly, this first large-scale comparative assessment of the antimicrobial effects of oxylipins reveals that regulators of plant defense responses are also the most active oxylipins against eukaryotic microorganisms, suggesting that such oxylipins might contribute to plant defense through their effects both on the plant and on pathogens, possibly through related mechanisms.
377 citations
TL;DR: This work identifies LEKTI as a key regulator of epidermal protease activity and degradation of desmoglein 1 as the primary pathogenic event in Netherton syndrome.
Abstract: Mutations in SPINK5, encoding the serine protease inhibitor LEKTI, cause Netherton syndrome, a severe autosomal recessive genodermatosis. Spink5(-/-) mice faithfully replicate key features of Netherton syndrome, including altered desquamation, impaired keratinization, hair malformation and a skin barrier defect. LEKTI deficiency causes abnormal desmosome cleavage in the upper granular layer through degradation of desmoglein 1 due to stratum corneum tryptic enzyme and stratum corneum chymotryptic enzyme-like hyperactivity. This leads to defective stratum corneum adhesion and resultant loss of skin barrier function. Profilaggrin processing is increased and implicates LEKTI in the cornification process. This work identifies LEKTI as a key regulator of epidermal protease activity and degradation of desmoglein 1 as the primary pathogenic event in Netherton syndrome.
359 citations
TL;DR: The results provide the anatomical pathway for multisensory integration at low levels of information processing in the primate and argue against a strict hierarchical model.
Abstract: While multisensory integration is thought to occur in higher hierarchical cortical areas, recent studies in man and monkey have revealed plurisensory modulations of activity in areas previously thought to be unimodal. To determine the cortical network involved in multisensory interactions, we performed multiple injections of different retrograde tracers in unimodal auditory (core), somatosensory (1/3b) and visual (V2 and MT) cortical areas of the marmoset. We found three types of heteromodal connections linking unimodal sensory areas. Visuo-somatosensory projections were observed originating from visual areas [probably the ventral and dorsal fundus of the superior temporal area (FSTv and FSTd), and middle temporal crescent (MTc)] toward areas 1/3b. Somatosensory projections to the auditory cortex were present from S2 and the anterior bank of the lateral sulcus. Finally, a visuo-auditory projection arises from an area anterior to the superior temporal sulcus (STS) toward the auditory core. Injections in different sensory regions allow us to define the frontal convexity and the temporal opercular caudal cortex as putative polysensory areas. A quantitative analysis of the laminar distribution of projecting neurons showed that heteromodal connections could be either feedback or feedforward. Taken together, our results provide the anatomical pathway for multisensory integration at low levels of information processing in the primate and argue against a strict hierarchical model.
355 citations
TL;DR: In this article, the fundamental electronic and magnetic properties of metal clusters deposited on surfaces and in matrices are discussed. And the influence of capping layers and deposition into matrices is discussed.
341 citations
TL;DR: It is shown that Nod factors increase mycorrhizal colonization and stimulate lateral root formation and the idea that this diffusible fungal factor might correspond to a previously hypothesized mycor rhizobium-legume signal, the 'Myc factor', is discussed.
Abstract: Legumes form two different types of intracellular root symbioses, with fungi and bacteria, resulting in arbuscular mycorrhiza and nitrogen-fixing nodules, respectively. Rhizobial signalling molecules, called Nod factors, play a key role in establishing the rhizobium-legume association and genes have been identified in Medicago truncatula that control a Nod factor signalling pathway leading to nodulation. Three of these genes, the so-called DMI1, DMI2 and DMI3 genes, are also required for formation of mycorrhiza, indicating that the symbiotic pathways activated by both the bacterial and the fungal symbionts share common steps. To analyse possible cross-talk between these pathways we have studied the effect of treatment with Nod factors on mycorrhization in M. truncatula. We show that Nod factors increase mycorrhizal colonization and stimulate lateral root formation. The stimulation of lateral root formation by Nod factors requires both the same structural features of Nod factors and the same plant genes (NFP, DMI1, DMI2, DMI3 and NSP1) that are required for other Nod factor-induced symbiotic responses such as early nodulin gene induction and cortical cell division. A diffusible factor from arbuscular mycorrhizal fungi was also found to stimulate lateral root formation, while three root pathogens did not have the same effect. Lateral root formation induced by fungal signal(s) was found to require the DMI1 and DMI2 genes, but not DMI3. The idea that this diffusible fungal factor might correspond to a previously hypothesized mycorrhizal signal, the 'Myc factor', is discussed.
337 citations
13 Mar 2005
TL;DR: In this paper, a nonsmooth optimization technique is proposed to solve H∞ synthesis problems under additional structural constraints on the controller, which avoids the use of Lyapunov variables and therefore leads to moderate size optimization programs even for very large systems.
Abstract: We develop nonsmooth optimization techniques to solve H∞ synthesis problems under additional structural constraints on the controller. Our approach avoids the use of Lyapunov variables and therefore leads to moderate size optimization programs even for very large systems. The proposed framework is very versatile and can accommodate a number of challenging design problems including static, fixed-order, fixed-structure, decentralized control, design of PID controllers and simultaneous design and stabilization problems. Our algorithmic strategy uses generalized gradients and bundling techniques suited for the H∞-norm and other nonsmooth performance criteria. Convergence to a critical point from an arbitrary starting point is proved (full version) and numerical tests are included to validate our methods.
TL;DR: In this article, the authors studied fine properties of quasiplurisubharmonic functions on compact Kahler manifolds and showed that locally pluripolar sets are globally quasi-pluripolar.
Abstract: We study fine properties of quasiplurisubharmonic functions on compact Kahler manifolds. We define and study several intrinsic capacities which characterize pluripolar sets and show that locally pluripolar sets are globally “quasi-pluripolar.”
TL;DR: This paper is a plea for a clarification of terminology, based on mathematical resemblances and the comparison of motivations between ''intuitionistic fuzzy sets'' and other theories.
06 Jul 2005
TL;DR: This paper extends the basic abstract argumentation framework, by taking into account two independent kinds of interaction between arguments: a defeat relation and a support relation, and proposes new semantics defined from characteristic properties that a set of arguments must satisfy in order to be an output of the argumentation process.
Abstract: In this paper, we extend the basic abstract argumentation framework proposed by Dung, by taking into account two independent kinds of interaction between arguments: a defeat relation and a support relation. In that new framework, called a bipolar argumentation framework, we focus on the concept of acceptability and propose new semantics defined from characteristic properties that a set of arguments must satisfy in order to be an output of the argumentation process. We generalize the well-known stable and preferred semantics by enforcing the coherence requirement for an acceptable set of arguments.
TL;DR: It is shown that brain GLP-1 controlled whole-body glucose fate during hyperglycemic conditions and inhibited muscle glucose utilization and increased insulin secretion to favor hepatic glycogen stores, preparing efficiently for the next fasting state.
Abstract: Intestinal glucagon-like peptide-1 (GLP-1) is a hormone released into the hepatoportal circulation that stimulates pancreatic insulin secretion. GLP-1 also acts as a neuropeptide to control food intake and cardiovascular functions, but its neural role in glucose homeostasis is unknown. We show that brain GLP-1 controlled whole-body glucose fate during hyperglycemic conditions. In mice undergoing a hyperglycemic hyperinsulinemic clamp, icv administration of the specific GLP-1 receptor antagonist exendin 9-39 (Ex9) increased muscle glucose utilization and glycogen content. This effect did not require muscle insulin action, as it also occurred in muscle insulin receptor KO mice. Conversely, icv infusion of the GLP-1 receptor agonist exendin 4 (Ex4) reduced insulin-stimulated muscle glucose utilization. In hyperglycemia achieved by i.v. infusion of glucose, icv Ex4, but not Ex9, caused a 4-fold increase in insulin secretion and enhanced liver glycogen storage. However, when glucose was infused intragastrically, icv Ex9 infusion lowered insulin secretion and hepatic glycogen levels, whereas no effects of icv Ex4 were observed. In diabetic mice fed a high-fat diet, a 1-month chronic i.p. Ex9 treatment improved glucose tolerance and fasting glycemia. Our data show that during hyperglycemia, brain GLP-1 inhibited muscle glucose utilization and increased insulin secretion to favor hepatic glycogen stores, preparing efficiently for the next fasting state.
TL;DR: In this paper, the knowledge about machining of nonconducting materials using electrochemical discharge phenomenon is reviewed up to this date with some particular attention to the electrochemical point of view.
Abstract: Machining with electrochemical discharges is an unconventional technology able to machine several electrically non-conductive materials like glass or some ceramics. After almost 40 years of its first mention in literature, this technology remains an academic application and was never applied in industrial context. The knowledge about machining of non-conducting materials using electrochemical discharge phenomenon is reviewed up to this date with some particular attention to the electrochemical point of view. Some main limiting factors are highlighted and possible solutions are discussed.
TL;DR: A new blind source separation (BSS) method called Time-Frequency Ratio Of Mixtures (TIFROM) which uses time-frequency information to cancel source signal contributions from a set of linear instantaneous mixtures of these sources.
TL;DR: In this paper, the authors study the large-scale topology and dynamics of maps of alliances in a major segment of the biotechnology industry and show that the network is scale-free.
TL;DR: It is concluded that functional group and carbon-chain length are inner dimensions of the honeybee olfactory space and that neural activity in the antennal lobe reflects the perceptual quality of odours.
Abstract: The question of whether or not neural activity patterns recorded in the olfactory centres of the brain correspond to olfactory perceptual measures remains unanswered. To address this question, we studied olfaction in honeybees Apis mellifera using the olfactory conditioning of the proboscis extension response. We conditioned bees to odours and tested generalisation responses to different odours. Sixteen odours were used, which varied both in their functional group (primary and secondary alcohols, aldehydes and ketones) and in their carbon-chain length (from six to nine carbons).The results obtained by presentation of a total of 16 × 16 odour pairs show that (i) all odorants presented could be learned, although acquisition was lower for short-chain ketones; (ii) generalisation varied depending both on the functional group and the carbon-chain length of odours trained; higher generalisation was found between long-chain than between short-chain molecules and between groups such as primary and secondary alcohols; (iii) for some odour pairs, cross-generalisation between odorants was asymmetric; (iv) a putative olfactory space could be defined for the honeybee with functional group and carbon-chain length as inner dimensions; (v) perceptual distances in such a space correlate well with physiological distances determined from optophysiological recordings of antennal lobe activity. We conclude that functional group and carbon-chain length are inner dimensions of the honeybee olfactory space and that neural activity in the antennal lobe reflects the perceptual quality of odours.
TL;DR: In this article, the notions of S-topologies, S-sites, and stacks over sites were introduced, and a model category of pre-stacks over a Grothendieck site was introduced.
TL;DR: In this article, the authors give the optimal conditions for the uniqueness of the positive L-invariant measure and the L 1 -uniqueness of the intrinsic Schrodinger operators on complete non-compact Riemannian manifolds.
TL;DR: In this article, the electrical characteristics of homogeneous dielectric barrier discharges in helium, argon and nitrogen are presented and discussed, including the time variation of the density of electron, ion, metastable state and electrical field.
Abstract: The electrical characteristics of homogeneous dielectric barrier discharges in helium, argon and nitrogen are presented and discussed. From the evolution of the discharge current as a function of the voltage applied to the gas it is shown that (i) in helium and argon, during the current increase, the discharge transits from a non-self-sustained discharge to a Townsend discharge and then a subnormal glow discharge (atmospheric pressure glow discharge) (ii) in nitrogen the ionization level is too low to induce a localization of the electrical field and the glow regime cannot be achieved. The discharge is a Townsend discharge (atmospheric pressure Townsend discharge). The characteristics of this specific discharge are described including the time variation of the density of electron, ion, metastable state and electrical field.
TL;DR: The present study demonstrates that adipocyte progenitor cells, i.e., the preadipocytes, are included in the CD34+/CD31− cell fraction, which displays distinct features from the adult mesenchymal and hematopoietic stem cells.
Abstract: The stroma-vascular fraction (SVF) of human adipose tissue has recently been described to be composed of endothelial cells identified as CD34+/CD31+ cells, infiltrated/resident macrophages defined as CD14+/CD31+ cells, and a new cell population characterized as CD34+/CD31- cells. To elucidate the cell identity of the adipocyte precursor cells, fluorescent activating cell sorter (FACS) analyses were performed on crude SVF cultured under adipogenic conditions, i.e., serum-deprived medium containing insulin, cortisol, triiodothyronine, and supplemented with a PPARgamma agonist for the first 3 days. The progressive accumulation of lipid droplets was associated with a selective enrichment of the CD34+/CD31- cell population whereas control experiments performed in medium supplemented with 10% serum showed an overall downregulation of the three cell markers without adipogenesis. Among the different cell subsets, the CD34+/CD31- subset was the unique cell fraction able to answer to adipogenic culture conditions. Indeed, a time-dependent expression of adipocyte markers as well as acquisition of adipocyte-typical metabolic activities were observed. In parallel, the gene expression of lipogenic and lipolytic enzymes increased. The ability to differentiate into adipocytes was restricted to cells that did not express the mesenchymal stem cell marker CD105. Furthermore, the CD34+/CD31- cells did not respond to culture conditions used for hematopoietic colony assays. Taken together, the present study demonstrates that adipocyte progenitor cells, i.e., the preadipocytes, are included in the CD34+/CD31- cell fraction, which displays distinct features from the adult mesenchymal and hematopoietic stem cells.
TL;DR: In this paper, the effect of alloying on the upper critical field was investigated for 12 C-alloyed films, in which disorder was introduced by growth, carbon doping or He-ion irradiation.
Abstract: We investigated the effect of alloying on the upper critical field ${H}_{c2}$ for 12 $\mathrm{Mg}{\mathrm{B}}_{2}$ films, in which disorder was introduced by growth, carbon doping or He-ion irradiation, finding a significant ${H}_{c2}$ enhancement in C-alloyed films, and an anomalous upward curvature of ${H}_{c2}(T)$. Record high values of $H_{c2}{}^{\ensuremath{\perp}}(4.2)\ensuremath{\approx}35\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ and $H_{c2}{}^{\ensuremath{\Vert}}(4.2)\ensuremath{\approx}51\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ were observed perpendicular and parallel to the $ab$ plane, respectively. The temperature dependence of ${H}_{c2}(T)$ is described well by a theory of dirty two-gap superconductivity. Extrapolation of the experimental data to $T=0$ suggests that $H_{c2}{}^{\ensuremath{\Vert}}(0)$ may approach the paramagnetic limit of $\ensuremath{\sim}70\phantom{\rule{0.3em}{0ex}}\mathrm{T}$.
TL;DR: Evidence is supported that aggregation relies on mechanisms of amplification, supported by interactions between individuals that follow simple rules based on local information and without knowledge of the global structure.
TL;DR: Comparison of the cell wall proteome of rosettes with the previously published cell wall proteins of cell suspension cultures showed a high level of cell specificity, especially for the different members of several large multigenic families.
Abstract: Weakly bound cell wall proteins of Arabidopsis thaliana were identified using a proteomic and bioinformatic approach. An efficient protocol of extraction based on vacuum-infiltration of the tissues was developed. Several salts and a chelating agent were compared for their ability to extract cell wall proteins without releasing cytoplasmic contaminants. Of the 93 proteins that were identified, a large proportion (60%) was released by calcium chloride. From bioinformatics analysis, it may be predicted that most of them (87 out of 93) had a signal peptide, whereas only six originated from the cytoplasm. Among the putative apoplastic proteins, a high proportion (67 out of 87) had a basic pI. Numerous glycoside hydrolases and proteins with interacting domains were identified, in agreement with the expected role of the extracellular matrix in polysaccharide metabolism and recognition phenomena. Ten proteinases were also found as well as six proteins with unknown functions. Comparison of the cell wall proteome of rosettes with the previously published cell wall proteome of cell suspension cultures showed a high level of cell specificity, especially for the different members of several large multigenic families.
TL;DR: A finite volume method based on the integration of the Laplace equation on both the cells of a primal almost arbitrary two-dimensional mesh and those of a dual mesh obtained by joining the centers of the cells, generally called "diamond-cells", of a third mesh is presented.
Abstract: We present a finite volume method based on the integration of the Laplace equation on both the cells of a primal almost arbitrary two-dimensional mesh and those of a dual mesh obtained by joining the centers of the cells of the primal mesh. The key ingredient is the definition of discrete gradient and divergence operators verifying a discrete Green formula. This method generalizes an existing finite volume method that requires "Voronoi-type" meshes. We show the equivalence of this finite volume method with a non-conforming finite element method with basis functions being P 1 on the cells, generally called "diamond-cells", of a third mesh. Under geometrical conditions on these diamond- cells, we prove a first-order convergence both in the H 1 norm and in the L 2 norm. Superconvergence results are obtained on certain types of homothetically refined grids. Finally, numerical experiments confirm these results and also show second-order convergence in the L 2 norm on general grids. They also indicate that this method performs particularly well for the approximation of the gradient of the solution, and may be used on degenerating triangular grids. An example of application on non- conforming locally refined grids is given.
TL;DR: In this paper, a singular value decomposition method with a Monte Carlo search algorithm was used to analyse the mid- infrared ISOCAMspectral maps of photodissociation regions (PDRs) in NGC 7023 and ρ Oph-SR3.
Abstract: We have coupled a singular value decomposition method with a Monte Carlo search algorithm to analyse the mid- infrared ISOCAMspectral maps of photodissociation regions (PDRs) in NGC 7023 and ρ Oph-SR3.Three different spectra and their associated spatial distribution were extracted from this analysis. It is shown that they can be associated with polycyclic aromatic hydrocarbons (PAHs) in their cationic and neutral forms and a third population of carbonaceous very small grains (VSGs). The method allows for the first time (i) to separate the contribution of neutral PAHs to the interstellar emission spectrum from that of cationic PAHs; (ii) to show that the 7.8 µm component of the "7.7 µm" broad feature is carried by VSGs, whereas the 7.6 µm component is due to PAHs; and (iii) to give evidence that free-flying PAHs are produced in PDRs by photoevaporation of VSGs. It is proposed that these carbonaceous VSGs are indeed PAH clusters. We derived a minimal size of 400 carbon atoms per cluster and estimated a UV absorption power of the order of 10 −24 WC −1 for their dissociation.
TL;DR: A Chapman-Enskog expansion is used to derive hyperbolic models for chemosensitive movements as a hydrodynamic limit of a velocity-jump process, providing a unified framework which includes previous models obtained by ad hoc methods or methods of moments.
Abstract: A Chapman-Enskog expansion is used to derive hyperbolic models for chemosensitive movements as a hydrodynamic limit of a velocity-jump process. On the one hand, it connects parabolic and hyperbolic chemotaxis models since the former arise as diffusion limits of a similar velocity-jump process. On the other hand, this approach provides a unified framework which includes previous models obtained by ad hoc methods or methods of moments. Numerical simulations are also performed and are motivated by recent experiments with human endothelial cells on matrigel. Their movements lead to the formation of networks that are interpreted as the beginning of a vasculature. These structures cannot be explained by parabolic models but are recovered by numerical experiments on hyperbolic models. Our kinetic model suggests that some kind of local interactions might be enough to explain them.
TL;DR: In this paper, an in situ Raman spectroscopy study of oxidation-induced changes in the structure and composition of double-wall carbon nanotubes (DWCNTs) was presented.