The Dynamic Formation of Prominence Condensations

We present simulations of a model for the formation of a prominence condensation in a coronal loop. The key idea behind the model is that the spatial localization of loop heating near the chromosphere leads to a catastrophic cooling in the corona (Antiochos & Klimchuk 1991). Using a new adaptive grid code, we simulate the complete growth of a condensation, and find that after approx. 5,000 s it reaches a quasi-steady state. We show that the size and the growth time of the condensation are in good agreement with data, and discuss the implications of the model for coronal heating and SOHO/TRACE observations.Comment: Astrophysical Journal latex file, 20 pages, 7 b-w figures (gif files

On the importance of 3D stress state in 2D earthquake rupture simulations with off-fault deformation

During the last decades, many numerical models have been developed to investigate the conditions for seismic and aseismic slip. Those models explore the behavior of frictional faults, embedded in either elastic or inelastic mediums, and submitted to a far field loading (seismic cycle models), or initial stresses (single dynamic rupture models). Those initial conditions impact both on-fault and off-fault dynamics. Because of the sparsity of direct measurements of fault stresses, modelers have to make assumptions about these initial conditions. To this day, Anderson's theory is the only framework that can be used to link fault generation and reactivation to the three-dimensional stress field. In this work we look at the role of the three dimensional stress field in modelling a 2D strike-slip fault under plane-strain conditions. We show that setting up the incorrect initial stress field, based on Anderson's theory, can lead to underestimation of the damage zone width by up to a factor of six, for the studied cases. Moreover, because of the interactions between fault slip and off-fault deformation, initial stress field influences the rupture propagation. Our study emphasizes the need to set up the correct initial 3D stress field, even in 2D numerical simulations

Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechanical performance

This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PLA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PLA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystallization during DSC and DMTA measurements, which enthalpy increased with each reprocessing step, suggested chain scission due to thermo-mechanical degradation. The effect of chain shortening on the glass-rubber relaxation studied by DMTA showed an increase in free volume affecting the segmental dynamics of PLA, particularly after the application of the second reprocessing step, in connection to the overall loss of performance showed by the remaining properties

Thermal analysis as a quality tool for assessing the influence of thermo-mechanical degradation on recycled poly(ethylene terephthalate)

Mechanical recycling of poly(ethylene terephthalate) (PET) was simulated by multiple processing to assess the effects of thermo-mechanical degradation, and characterized using rheological and thermal analysis techniques. Thermo-mechanical degradation under repeated extrusion induces chain scission reactions in PET, which result in a dramatic loss in the deformation capabilities and an increase in the fluidity of the polymer under reprocessing, reducing its recycling possibilities after four extrusion cycles. Multiple reprocessing severely affects the storage modulus and the microstructure of recycled PET, both in the amorphous and crystalline regions. Multimodal melting behavior is observed for reprocessed PET, indicating heterogeneous and segregated crystalline regions. A deconvolution procedure has been applied to individually characterize each crystalline population in terms of lamellar thickness distribution and partial crystallinity. Thermal analysis techniques such as differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA) have proved to be suitable techniques for the quality assessment of recycled PET, giving unequivocal information about its degree of degradation compared to the common technological measurements of melt-mass flow rate (MFR) or oxidative stability (TOx)

Comparison of Lures Loaded with Codlemone and Pear Ester for Capturing Codling Moths, Cydia pomonella, in Apple and Pear Orchards using Mating Disruption

Studies were conducted in apple, Malus domestica Borkhausen and pear, Pyrus communis L. (Rosales: Rosaceae), orchards to evaluate the attractiveness of grey halobutyl septa loaded with 1 (L2) and 10 (Mega) mg of codlemone, 8E, 10E-dodecadien-1-ol, 3 mg of pear ester, ethyl (E,Z)-2,4-decadienoate (DA2313), and 3 mg of pear ester plus 3 mg of codlemone (Combo) to adult codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). All studies were conducted in orchards treated with pheromone mating disruption. All four lures were tested on diamond-shaped sticky traps placed in 60 plots of apple and 40 plots of pears in 2003/04, and in 62 plots of apples and 30 of pears in 2004–05. Combo lures attracted significantly more moths (males + females) than all the others in both years. Comparisons among flights showed significant differences mainly for flight 1 and 2, but not always for flight 3. Mega lures provided no significant improvement compared with L2 lures during both seasons regarding the total number of moths. Combo and DA2313 lures attracted fewer females than males during the whole season. For most sample dates, more virgin than mated females were attracted to Combo lures, except during the third flight, and the overall ratio was 60:40, although the difference was not statistically significant. We conclude that the Combo lures are better indicators of codling moth activity in pheromone treated orchards, regardless of pest population level, when compared with similar lures containing codlemone or pear ester alone

Analysis of Poly(thiourethane) Covalent Adaptable Network through Broadband Dielectric Spectroscopy

[EN] The dielectric spectra of the poly(thiourethane) network, HDI-S3, have been analyzed to know the nature and the cooperativity of each of the six dielectric processes observed. At low temperatures, ¿1, ¿2, and ß dielectric relaxations were attributed to noncooperative local motions in the glassy state, in which apparent activation energies are 30, 36, and 60 kJ·mol¿1, respectively. At higher temperatures, three dielectric relaxations are observed (¿Tg, ¿*, ¿). The ¿Tg relaxation is attributed to the glass transition, and it is overlapped with the ¿* relaxation. The molecular origin of ¿* relaxation is associated with the bond exchange reaction. Finally, the ¿ relaxation is ascribed to the heterogeneity of the sample although its origin is uncertain. The DC conductivity (¿DC) is found to be an appropriate variable to analyze the bond exchange reaction. Accordingly, the HDI-S3 has a molecular exchange mechanism of dissociative nature.The authors would like to thank the support of the European Union through the European Regional Development Funds (ERDF) and the Spanish Ministry of Science and Innovation for the research projects POLYELMETH (PID2020-116322RB-C31) and MCIN/AEI/10.13039/201100011033, which financed the PID2020/115102RB-C21 project, and the Generalitat de Catalunya for the 2017-SGR-77. This study forms part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.11) and by Generalitat Valenciana.Pascual-Jose, B.; De La Flor, S.; Serra, A.; Ribes-Greus, A. (2023). Analysis of Poly(thiourethane) Covalent Adaptable Network through Broadband Dielectric Spectroscopy. ACS Applied Polymer Materials. 5(2):1125-1134. https://doi.org/10.1021/acsapm.2c01543112511345

ES cells-derived ectomesenchymal cells for tooth engineering.

Recent progresses in stem cell biology and tissue engineering allow considering the possible development of new therapies for compensating the dental tissue losses associated with traumas, pathologies or ageing. The possibility of generating a tooth by mimicking development through reassociations between dental epithelial cells and ectomesenchymal cells derived from the neural crest (NC) has been demonstrated in the mouse. In the search of cell sources to be used for a human transfer, pluripotent stem cells could represent a good alternative. Our study thus focuses on obtaining, ectomesenchymal cells from pluripotent ES cells, capable of promoting tooth histomorphogenesis, when reassociated with a competent dental epithelium. To this end, two ES differentiation protocols, using cyclopamine or a combination of FGF2 and BMP4, have been developed and tested for their capacity to generate such cells. The differentiated ES cells were characterized by quantitative RT-PCR. Both protocols led the cells to acquire in 10 days a mesenchymal-like cell morphology. Rapidly after induction, the cells loose their expression of pluripotent genes while sequentially activating typical NC specifiers. However, the kinetics of gene activation differed between the 2 protocols. Interestingly, Twist, a gene whose expression in the NC is associated with a commitment towards an ectomesenchymal fate, is only activated under the influence of FGF2 and BMP4. Reassociation experiments with a competent epithelium will allow testing the odontogenic potential of the differentiated ES cells. These experiments performed in the mouse system should allow defining a strategy for obtaining odontogenic competent human cells. Les progrès en matière de biologie de cellules souches et d’ingénierie tissulaire permettent d’envisager le développement de nouvelles thérapies pour pallier les pertes de tissus dentaires consécutives à des traumatismes, des situations pathologiques ou au vieillissement. La possibilité de générer une dent en mimant le développement, par réassociations entre cellules dentaires épithéliales et mésenchymateuses dérivées des crêtes neurales (CN), a été démontrée chez la souris. Dans la recherche de ressources cellulaires utilisables pour un transfert chez l’homme, les cellules souches pluripotentes pourraient constituer une alternative. Notre but est d’obtenir à partir de ces dernières, des cellules ectomésenchymateuses capables d’interagir avec un épithélium dentaire pour promouvoir l’histomorphogenèse d’une dent. Pour cela, deux protocoles de différenciation de cellules ES, utilisant la cyclopamine ou une combinaison de FGF2/BMP4, ont été mis au point. Les cellules induites ont été caractérisées par PCR quantitative. Les deux protocoles de différenciation amènent les cellules à acquérir en 10 jours, une morphologie de type mésenchymateux. Après induction, l’expression des gènes de pluripotence chute de façon drastique alors que celle des gènes spécificateurs de CN est activée. Toutefois, la cinétique varie selon le protocole. Le gène Twist, dont l’expression dans les CN est associée à un engagement vers l’ectomésenchyme, n’est activé significativement que sous l’action de FGF2/BMP4. Des expériences de réassociations avec un épithélium dentaire sont en cours pour évaluer le potentiel odontogène des cellules ES différenciées. A terme, ces approches menées chez la souris devraient permettre de définir une stratégie pour l’obtention de cellules compétentes humaines.Recent progresses in stem cell biology and tissue engineering allow considering the possible development of new therapies for compensating the dental tissue losses associated with traumas, pathologies or ageing. The possibility of generating a tooth by mimicking development through reassociations between dental epithelial cells and ectomesenchymal cells derived from the neural crest (NC) has been demonstrated in the mouse. In the search of cell sources to be used for a human transfer, pluripotent stem cells could represent a good alternative. Our study thus focuses on obtaining, ectomesenchymal cells from pluripotent ES cells, capable of promoting tooth histomorphogenesis, when reassociated with a competent dental epithelium. To this end, two ES differentiation protocols, using cyclopamine or a combination of FGF2 and BMP4, have been developed and tested for their capacity to generate such cells. The differentiated ES cells were characterized by quantitative RT-PCR. Both protocols led the cells to acquire in 10 days a mesenchymal-like cell morphology. Rapidly after induction, the cells loose their expression of pluripotent genes while sequentially activating typical NC specifiers. However, the kinetics of gene activation differed between the 2 protocols. Interestingly, Twist, a gene whose expression in the NC is associated with a commitment towards an ectomesenchymal fate, is only activated under the influence of FGF2 and BMP4. Reassociation experiments with a competent epithelium will allow testing the odontogenic potential of the differentiated ES cells. These experiments performed in the mouse system should allow defining a strategy for obtaining odontogenic competent human cells. Les progrès en matière de biologie de cellules souches et d’ingénierie tissulaire permettent d’envisager le développement de nouvelles thérapies pour pallier les pertes de tissus dentaires consécutives à des traumatismes, des situations pathologiques ou au vieillissement. La possibilité de générer une dent en mimant le développement, par réassociations entre cellules dentaires épithéliales et mésenchymateuses dérivées des crêtes neurales (CN), a été démontrée chez la souris. Dans la recherche de ressources cellulaires utilisables pour un transfert chez l’homme, les cellules souches pluripotentes pourraient constituer une alternative. Notre but est d’obtenir à partir de ces dernières, des cellules ectomésenchymateuses capables d’interagir avec un épithélium dentaire pour promouvoir l’histomorphogenèse d’une dent. Pour cela, deux protocoles de différenciation de cellules ES, utilisant la cyclopamine ou une combinaison de FGF2/BMP4, ont été mis au point. Les cellules induites ont été caractérisées par PCR quantitative. Les deux protocoles de différenciation amènent les cellules à acquérir en 10 jours, une morphologie de type mésenchymateux. Après induction, l’expression des gènes de pluripotence chute de façon drastique alors que celle des gènes spécificateurs de CN est activée. Toutefois, la cinétique varie selon le protocole. Le gène Twist, dont l’expression dans les CN est associée à un engagement vers l’ectomésenchyme, n’est activé significativement que sous l’action de FGF2/BMP4. Des expériences de réassociations avec un épithélium dentaire sont en cours pour évaluer le potentiel odontogène des cellules ES différenciées. A terme, ces approches menées chez la souris devraient permettre de définir une stratégie pour l’obtention de cellules compétentes humaines

Agelastatin A, a new skeleton cytotoxic alkaloid of the oroidin family : isolation from the Axinellid sponge Agelas dendromorpha of the Coral Sea

Agelastatin A, isolated from the axinellid sponge #Agelas dendromorpha$ of the Coral Sea, is a new skeleton alkaloid with, unusually for the oroidin family to which it belongs, marked cytototoxicity toward tumour cells in culture. (Résumé d'auteur

Effect of the dissolution time into an acid hydrolytic solvent to taylor electrospun nanofibrous polycaprolactone scaffolds

The hydrolysis of the polycaprolactone (PCL) as a function of the dissolution time in a formic/ acetic acid mixture was considered as a method for tailoring the morphology of nanofibrous PCL scaffolds. Hence, the aim of this research was to establish a correlation between the dissolution time of the polymer in the acid solvent with the physicochemical properties of the electrospun nanofibrous scaffolds and their further service life behaviour. The physico-chemical properties of the scaffolds were assessed in terms of fibre morphology, molar mass and thermal behaviour. A reduction of the molar mass and the lamellar thickness as well as an increase of the crystallinity degree were observed as a function of dissolution time. Bead-free fibres were found after 24 and 48 h of dissolution time, with similar diameter distributions. The decrease of the fibre diameter distributions along with the apparition of beads was especially significant for scaffolds prepared after 72 h and 120 h of dissolution time in the acid mixture. The service life of the obtained devices was evaluated by means of in vitro validation under abiotic physiological conditions. All the scaffolds maintained the nanofibrous structure after 100 days of immersion in water and PBS. The molar mass was barely affected and the crystallinity degree and the lamellar thickness increased along immersion, preventing scaffolds from degradation. Scaffolds prepared after 24 h and 48 h kept their fibre diameters, whereas those prepared after 72 h and 120 h showed a significant reduction. This PCL tailoring procedure to obtain scaffolds that maintain the nanoscaled structure after such long in vitro evaluation will bring new opportunities in the design of longterm biomedical patches