Detectability of the 21 cm-CMB cross-correlation from the EoR

The 21-cm line fluctuations and the cosmic microwave background (CMB) are powerful probes of the epoch of reionisation of the universe. We study the potential of the cross-correlation between 21-cm line fluctuations and CMB anisotropy to obtain further constraints on the reionisation history. We compute analytically the 21-cm cross-correlation with the CMB temperature anisotropy and polarisation, and we calculate the signal-to-noise (SN) ratio for its detection with Planck together with LOFAR, MWA and SKA. We find, on the one hand, that the 21-cm cross-correlation signal with CMB polarisation from the instant reionisation can be detected with an SN ratio of $\sim 1$ for LOFAR and $\sim 10$ for SKA. On the other hand, we confirm that the detection of the 21-cm cross-correlation with CMB polarisation is practically infeasible.Comment: 12 figure

The cross-correlation of the CMB polarisation and the 21-cm line fluctuations from cosmic reionisation

The cosmic microwave background (CMB) polarisation and the 21 cm line fluctuations are powerful probes of cosmological reionisation. We study how the cross-correlation between the CMB polarisation (E-modes) and the 21 cm line fluctuations can be used to gain further understanding of the reionisation history, within the framework of inhomogeneous reionisation. Since the E-mode polarisation reflects the amplitude of the quadrupole component of the CMB temperature fluctuations, the angular power spectrum of the cross-correlation exhibits oscillations at all multipoles. The first peak of the power spectrum appears at the scale corresponding to the quadrupole at the redshift that is probed by the 21 cm line fluctuations. The peak reaches its maximum value in redshift when the average ionisation fraction of the universe is about half. On the other hand, on small scales, there is a damping that depends on the duration of reionisation. Thus, the cross-correlation between the CMB polarisation and the 21 cm line fluctuations has the potential to constrain accurately the epoch and the duration of reionisation

Low-mass pre--main-sequence stars in the Magellanic Clouds

[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar stars form in very large numbers. Most attractive places for catching low-mass star formation in the act are young stellar clusters and associations, still (half-)embedded in star-forming regions. The low-mass stars in such regions are still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature of these objects and the contamination of their samples by the evolved populations of the Galactic disk impose demanding observational techniques for the detection of complete numbers of PMS stars in the Milky Way. The Magellanic Clouds, the companion galaxies to our own, demonstrate an exceptional star formation activity. The low extinction and stellar field contamination in star-forming regions of these galaxies imply a more efficient detection of low-mass PMS stars than in the Milky Way, but their distance from us make the application of special detection techniques unfeasible. Nonetheless, imaging with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of such objects are identified as the low-mass stellar content of their star-forming regions, changing completely our picture of young stellar systems outside the Milky Way, and extending the extragalactic stellar IMF below the persisting threshold of a few solar masses. This review presents the recent developments in the investigation of PMS stars in the Magellanic Clouds, with special focus on the limitations by single-epoch photometry that can only be circumvented by the detailed study of the observable behavior of these stars in the color-magnitude diagram. The achieved characterization of the low-mass PMS stars in the Magellanic Clouds allowed thus a more comprehensive understanding of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4 figures. Accepted for publication in Space Science Review

Hydrogels adaptatifs stimuli-sensibles (temperature et lumière) à base d'acide hyaluronique (HA)

Hydrogels are soft materials made of a cross-linked hydrophilic polymer able to swell and to absorb a large amount of water. They are particularly applied in the biomedical field, which requires the use of biocompatible materials. Hyaluronic acid (HA), a glycosaminoglycan from the extracellular matrix, is a promising choice because of its biocompatibility and its numerous functional groups, which allow its cross-linking in order to obtain a hydrogel. This manuscript will therefore deal with its functionalization with stimuli-responsive moieties to achieve physical hydrogels by modifying its physico-chemical environment. Firstly, thermo-responsive hydrogels will be obtained by grafting polymers displaying a LCST onto hyaluronic acid. It will be realised first with a commercial polyetheramine, Jeffamine® M2005, which resulted in derivatives able to undergo a transition towards a hydrogel by raising the temperature, as evidenced by rheological measurements. However, the transitions were taking place above 37 °C. Therefore, the grafting of a Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline) synthesized in the lab was attempted through a one-pot reaction scheme. The tuning of the monomeric composition of the graft allowed a much better control of the hydrogel’s thermo-responsiveness, with transitions below 37 °C becoming achievable. Finally, a photo-responsive azobenzene moiety was also grafted on hyaluronic acid. Azobenzenes are able to shift from trans to cis conformation through exposure to UV-visible light of specific wavelengths. Their selective inclusion within α-cyclodextrin (α-CD), only possible with the trans conformation, will be evaluated as well as the possibility to design photo-responsive hydrogels by mixing HA-azobenzene with HA functionalized with α-CD.Les hydrogels sont des matériaux mous constitués d’un réseau de polymères hydrophiles réticulés capables d’absorber et de retenir un volume important d’eau. Ils trouvent de nombreuses applications dans le domaine biomédical, ce qui nécessite l’emploi de matériaux biocompatibles. Dans cette optique, l’acide hyaluronique (HA), un glycosaminoglycane de la matrice extracellulaire, est un candidat prometteur du fait de sa biocompatibilité et de la présence de nombreux groupes fonctionnels sur son unité disaccharide permettant de le réticuler pour obtenir des hydrogels. Ce manuscrit porte donc sur sa fonctionnalisation par des groupements stimuli-sensibles afin de lui permettre de former des hydrogels physiques en modifiant son environnement physico-chimique. Dans un premier temps, des hydrogels thermosensibles seront obtenus par le greffage de polymère à LCST. La fonctionnalisation sera réalisée dans un premier temps avec un polyétheramine commercial, la Jeffamine® M2005, qui a permis l’obtention de dérivés capables de former des hydrogels par élévation de la température, comme l’ont montré des mesures rhéologiques. Cependant, les transitions obtenues ont été observées à des températures plus élevées que 37 °C. Par la suite, un copolymère de Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline), synthétisé au laboratoire a été greffé sur l’acide hyaluronique selon une stratégie « one-pot ». L’ajustement possible de la composition du greffon a permis d’obtenir un meilleur contrôle des propriétés thermosensibles des hydrogels, avec une transition pouvant être inférieure à 37 °C. Finalement, une fonctionnalité azobenzène photosensible sera greffée sur l’acide hyaluronique. Elle peut passer d’une conformation trans apolaire à une conformation cis légèrement polaire et inversement par irradiation UV-visible à des longueurs d’ondes spécifiques. Leur inclusion sélective au sein des cavités d’α-cyclodextrine (α-CD), uniquement possible en conformation trans sera étudiée, ainsi que la possibilité de former des hydrogels en mélangeant les HA-azobenzene avec du HA fonctionnalisé avec de l’α-CD

Hydrogels adaptatifs stimuli-sensibles (temperature et lumière) à base d'acide hyaluronique (HA)

Hydrogels are soft materials made of a cross-linked hydrophilic polymer able to swell and to absorb a large amount of water. They are particularly applied in the biomedical field, which requires the use of biocompatible materials. Hyaluronic acid (HA), a glycosaminoglycan from the extracellular matrix, is a promising choice because of its biocompatibility and its numerous functional groups, which allow its cross-linking in order to obtain a hydrogel. This manuscript will therefore deal with its functionalization with stimuli-responsive moieties to achieve physical hydrogels by modifying its physico-chemical environment. Firstly, thermo-responsive hydrogels will be obtained by grafting polymers displaying a LCST onto hyaluronic acid. It will be realised first with a commercial polyetheramine, Jeffamine® M2005, which resulted in derivatives able to undergo a transition towards a hydrogel by raising the temperature, as evidenced by rheological measurements. However, the transitions were taking place above 37 °C. Therefore, the grafting of a Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline) synthesized in the lab was attempted through a one-pot reaction scheme. The tuning of the monomeric composition of the graft allowed a much better control of the hydrogel’s thermo-responsiveness, with transitions below 37 °C becoming achievable. Finally, a photo-responsive azobenzene moiety was also grafted on hyaluronic acid. Azobenzenes are able to shift from trans to cis conformation through exposure to UV-visible light of specific wavelengths. Their selective inclusion within α-cyclodextrin (α-CD), only possible with the trans conformation, will be evaluated as well as the possibility to design photo-responsive hydrogels by mixing HA-azobenzene with HA functionalized with α-CD.Les hydrogels sont des matériaux mous constitués d’un réseau de polymères hydrophiles réticulés capables d’absorber et de retenir un volume important d’eau. Ils trouvent de nombreuses applications dans le domaine biomédical, ce qui nécessite l’emploi de matériaux biocompatibles. Dans cette optique, l’acide hyaluronique (HA), un glycosaminoglycane de la matrice extracellulaire, est un candidat prometteur du fait de sa biocompatibilité et de la présence de nombreux groupes fonctionnels sur son unité disaccharide permettant de le réticuler pour obtenir des hydrogels. Ce manuscrit porte donc sur sa fonctionnalisation par des groupements stimuli-sensibles afin de lui permettre de former des hydrogels physiques en modifiant son environnement physico-chimique. Dans un premier temps, des hydrogels thermosensibles seront obtenus par le greffage de polymère à LCST. La fonctionnalisation sera réalisée dans un premier temps avec un polyétheramine commercial, la Jeffamine® M2005, qui a permis l’obtention de dérivés capables de former des hydrogels par élévation de la température, comme l’ont montré des mesures rhéologiques. Cependant, les transitions obtenues ont été observées à des températures plus élevées que 37 °C. Par la suite, un copolymère de Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline), synthétisé au laboratoire a été greffé sur l’acide hyaluronique selon une stratégie « one-pot ». L’ajustement possible de la composition du greffon a permis d’obtenir un meilleur contrôle des propriétés thermosensibles des hydrogels, avec une transition pouvant être inférieure à 37 °C. Finalement, une fonctionnalité azobenzène photosensible sera greffée sur l’acide hyaluronique. Elle peut passer d’une conformation trans apolaire à une conformation cis légèrement polaire et inversement par irradiation UV-visible à des longueurs d’ondes spécifiques. Leur inclusion sélective au sein des cavités d’α-cyclodextrine (α-CD), uniquement possible en conformation trans sera étudiée, ainsi que la possibilité de former des hydrogels en mélangeant les HA-azobenzene avec du HA fonctionnalisé avec de l’α-CD

Hyaluronic acid (HA) based adaptative stimuli-responsive hydrogels (temperature and light)

Les hydrogels sont des matériaux mous constitués d’un réseau de polymères hydrophiles réticulés capables d’absorber et de retenir un volume important d’eau. Ils trouvent de nombreuses applications dans le domaine biomédical, ce qui nécessite l’emploi de matériaux biocompatibles. Dans cette optique, l’acide hyaluronique (HA), un glycosaminoglycane de la matrice extracellulaire, est un candidat prometteur du fait de sa biocompatibilité et de la présence de nombreux groupes fonctionnels sur son unité disaccharide permettant de le réticuler pour obtenir des hydrogels. Ce manuscrit porte donc sur sa fonctionnalisation par des groupements stimuli-sensibles afin de lui permettre de former des hydrogels physiques en modifiant son environnement physico-chimique. Dans un premier temps, des hydrogels thermosensibles seront obtenus par le greffage de polymère à LCST. La fonctionnalisation sera réalisée dans un premier temps avec un polyétheramine commercial, la Jeffamine® M2005, qui a permis l’obtention de dérivés capables de former des hydrogels par élévation de la température, comme l’ont montré des mesures rhéologiques. Cependant, les transitions obtenues ont été observées à des températures plus élevées que 37 °C. Par la suite, un copolymère de Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline), synthétisé au laboratoire a été greffé sur l’acide hyaluronique selon une stratégie « one-pot ». L’ajustement possible de la composition du greffon a permis d’obtenir un meilleur contrôle des propriétés thermosensibles des hydrogels, avec une transition pouvant être inférieure à 37 °C. Finalement, une fonctionnalité azobenzène photosensible sera greffée sur l’acide hyaluronique. Elle peut passer d’une conformation trans apolaire à une conformation cis légèrement polaire et inversement par irradiation UV-visible à des longueurs d’ondes spécifiques. Leur inclusion sélective au sein des cavités d’α-cyclodextrine (α-CD), uniquement possible en conformation trans sera étudiée, ainsi que la possibilité de former des hydrogels en mélangeant les HA-azobenzene avec du HA fonctionnalisé avec de l’α-CD.Hydrogels are soft materials made of a cross-linked hydrophilic polymer able to swell and to absorb a large amount of water. They are particularly applied in the biomedical field, which requires the use of biocompatible materials. Hyaluronic acid (HA), a glycosaminoglycan from the extracellular matrix, is a promising choice because of its biocompatibility and its numerous functional groups, which allow its cross-linking in order to obtain a hydrogel. This manuscript will therefore deal with its functionalization with stimuli-responsive moieties to achieve physical hydrogels by modifying its physico-chemical environment. Firstly, thermo-responsive hydrogels will be obtained by grafting polymers displaying a LCST onto hyaluronic acid. It will be realised first with a commercial polyetheramine, Jeffamine® M2005, which resulted in derivatives able to undergo a transition towards a hydrogel by raising the temperature, as evidenced by rheological measurements. However, the transitions were taking place above 37 °C. Therefore, the grafting of a Poly(2-isopropyl-2-oxazoline)-co-Poly(2-n-butyl-2-oxazoline) synthesized in the lab was attempted through a one-pot reaction scheme. The tuning of the monomeric composition of the graft allowed a much better control of the hydrogel’s thermo-responsiveness, with transitions below 37 °C becoming achievable. Finally, a photo-responsive azobenzene moiety was also grafted on hyaluronic acid. Azobenzenes are able to shift from trans to cis conformation through exposure to UV-visible light of specific wavelengths. Their selective inclusion within α-cyclodextrin (α-CD), only possible with the trans conformation, will be evaluated as well as the possibility to design photo-responsive hydrogels by mixing HA-azobenzene with HA functionalized with α-CD

Hyaluronic Acid Functionalization with Jeffamine® M2005: A Comparison of the Thermo-Responsiveness Properties of the Hydrogel Obtained through Two Different Synthesis Routes

International audienceHyaluronic acid (HA) of different molar masses (respectively 38,000, 140,000 and 1,200,000 g.mol−1) have been functionalized with a commercial poly(etheramine), Jeffamine® M2005, in order to devise physical thermo-responsive hydrogels. Two routes have been studied, involving the use of either water for the first one or of N,N′-Dimethylformamide (DMF), a polar aprotic solvent, for the second one. In the case of the water route, the reaction was performed using a mixture of N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) as coupling reagents. The reaction was optimized while making sure no free M2005 remained in the final material, leading to M2005 grafting degrees of about 4%, which enabled the formation of hydrogels by increasing the temperature. In the case of the organic solvent route, propylphosphonic anhydride T3P® was used as a coupling reagent in DMF, resulting in a M2005 grafting degree of around 8% with better thermo-responsive properties of HA-g-M2005 compared to those obtained when the reaction was performed in water. However, the reaction systematically led to covalent cross-linking in the case of the HA, with the highest starting molar masses resulting in a very different rheological behaviour and with higher gel strength retaining thermo-responsive behaviour but being only poorly soluble in water

Thermo-responsive hydrogels from hyaluronic acid functionalized with poly(2-alkyl-2-oxazoline) copolymers with tuneable transition temperature

International audienc

A mild and straightforward one-pot hyaluronic acid functionalization through termination of poly-(2-alkyl-2-oxazoline)

International audienc

Critical survey of stability constants and related thermodynamic data of fluoride complexes in aqueous solution

The Universe's Epoch of Reionization can be studied using a number of observational probes that provide complementary or corroborating information. Each of these probes suffers from its own systematic and statistical uncertainties. It is therefore useful to consider the mutual information that these data sets contain. In this paper, we present a cross-correlation study between the kinetic Sunyaev-Zel'dovich effect - produced by the scattering of cosmic microwave background (CMB) photons off free electrons produced during the reionization process - and the cosmological 21 cm signal - which reflects the neutral hydrogen content of the Universe, as a function of redshift. The study is carried out using a simulated reionization history in 100 h(-1) Mpc scale N-body simulations with radiative transfer. In essence, we find that the two probes anticorrelate. The significance of the anticorrelation signal depends on the extent of the reionization process, wherein extended histories result in a much stronger signal compared to instantaneous cases. Unfortunately, however, once the primary CMB fluctuations are included into our simulation they serve as a source of large correlated noise that renders the cross-correlation signal insignificant, regardless of the reionization scenario