Thermally rearranged polybenzoxazoles made from poly(<i>ortho</i>-hydroxyamide)s. Characterization and evaluation as gas separation membranes

Dí,ez, Blanca,Cuadrado, Purificació,n,Marcos-Ferná,ndez, Á,ngel,de la Campa, José,G.,Tena, Alberto,Prá,danos, Pedro,Palacio, Laura,Lee, Young Moo,Alvarez, Cristina Elsevier 2018 Reactive & functional polymers Vol.127 No.-

<P><B>Abstract</B></P> <P>Two series of aromatic poly(<I>ortho</I>-hydroxyamide)s (poly(<I>o</I>-hydroxyamide)s, HPAs) were prepared by reaction of two diamines, 2,2-bis(3-amino-4-hydroxyphenyl) propane (APA) and 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (APAF), with four aromatic diacid chlorides; terephthaloyl dichloride (TPC), isophthaloyl dichloride (IPC), 2,2-bis[4-chlorocarbonylphenyl)hexafluoropropane (6FC) and 4,4′-sulfonyldibenzoyl dichloride (DBSC). Amorphous HPAs with high molecular weights (inherent viscosities higher than 0.5 dL/g) and relatively high glass transition temperatures (220–280 °C) were obtained. Dense membranes of HPAs were able to undergo a thermal rearrangement (TR) process to polybenzoxazoles (β-TR-PBOs) heating at moderate temperatures (between 250 and 375 °C), and their complete conversion was reached at a temperature below 375 °C, depending on the <I>o</I>-hydroxy diamine moiety, APA and APAF. The β-TR-PBOs films derived from APAF showed a higher thermal stability and higher Tg than those from APA. Gas separation properties of TR-PBOs membranes were superior to those of their poly(<I>o</I>-hydroxyamide) precursors, particularly for the following gas pairs: O<SUB>2</SUB>/N<SUB>2</SUB>, CO<SUB>2</SUB>/CH<SUB>4</SUB>, He/CH<SUB>4</SUB> and He/CO<SUB>2</SUB>.</P>

Crystal structure and second harmonic generation in Bi₂TeO₅: An X-N study from synchrotron and neutron diffraction data

Ló,pez, C.A.,Bâ,ati, E.,Ferná,ndez-Dí,az, M.T.,Saouma, F.O.,Jang, J.I.,Alonso, J.A. Academic Press 2019 Journal of solid state chemistry Vol.276 No.-

<P><B>Abstract</B></P> <P>Bi<SUB>2</SUB>TeO<SUB>5</SUB> has been obtained in polycrystalline form via solid state reaction and structurally characterized from both synchrotron and neutron powder diffraction data, enabling the precise determination of the atomic positions. The crystal structure is defined in the acentric <I>Amb</I>2 space group, containing three crystallographically unequivalent Bi atoms. The position of the stereochemically active electron lone pairs of both Bi<SUP>3+</SUP> and Te<SUP>4+</SUP> ions is inferred to be opposite to the strongly covalent BiO and TeO chemical bonds; the global electron polarization arises from the non-compensated Bi<SUP>3+</SUP> lone electron pairs. Additionally, from difference Fourier maps between synchrotron and neutron diffraction data (X-N technique) it was possible to observe experimental evidence of the lone electron pair for Bi<SUP>3+</SUP>. Nonlinear optical measurements display highly active second harmonic generation response, comparable to that of reference AgGaSe<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The crystal structure is defined in the non-centrosymmetric <I>Amb</I>2 space group. </LI> <LI> Fourier maps between synchrotron and neutron diffraction data (X-N technique). </LI> <LI> Experimental evidence of Bi<SUP>3+</SUP>lone electron pair from X-N study. </LI> <LI> Nonlinear optical measurements display highly active SHG response. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The pulsating hot subdwarf Balloon 090100001: results of the 2005 multisite campaign

Baran, A.,Oreiro, R.,Pigulski, A.,Herná,ndez, F. Pé,rez,Ulla, A.,Reed, M. D.,Rodr&iacute,guez-Ló,pez, C.,Moskalik, P.,Kim, S.-L.,Chen, W.-P.,Crowe, R.,Siwak, M.,Armendarez, L.,Binder Blackwell Publishing Ltd 2009 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.392 No.3

<P>ABSTRACT</P><P>We present the results of a multisite photometric campaign on the pulsating B-type hot subdwarf star Balloon 090100001 (Bal09). The star is one of the two known hybrid hot subdwarfs with both long- and short-period oscillations, theoretically attributed to <I>g</I> and <I>p</I> modes. The campaign involved eight telescopes with three obtaining <I>UBVR</I> data, four <I>B</I>-band data and one Strömgren <I>uvby</I> photometry. The campaign covered 48 nights, providing a temporal resolution of 0.36 μHz with a detection threshold of about 0.2 mmag in <I>B</I>-filter data.</P><P>Bal09 has the richest pulsation spectrum of any known pulsating subdwarf B star, and our analysis detected 114 frequencies including 97 independent and 17 combination ones. Most of the 24 <I>g</I>-mode frequencies are between 0.1 and 0.4 mHz. Of the remaining 73, presumably <I>p</I> modes, 72 group into four distinct regions near 2.8, 3.8, 4.7 and 5.5 mHz. The density of frequencies requires that some modes must have degrees ℓ larger than 2. The modes in the 2.8 mHz region have the largest amplitudes. The strongest mode (<I>f</I><SUB>1</SUB>) is most likely radial, while the remaining ones in this region form two nearly symmetric multiplets: a triplet and quintuplet, attributed to rotationally split ℓ= 1 and 2 modes, respectively. We find clear increases of splitting in both multiplets between the 2004 and 2005 observing campaigns, amounting to ∼15 per cent on average. The observed splittings imply that the rotational rate in Bal09 depends on stellar latitude and is the fastest on the equator. We also speculate on the possible reasons for the changes of splitting. The only plausible explanation we find is torsional oscillation. This hypothesis, however, needs to be verified in the future by detailed modelling. In this context, it is very important to monitor the splittings on a longer time-scale as their behaviour may help to explain this interesting phenomenon.</P><P>The amplitudes of almost all terms detected in both 2004 and 2005 were found to vary. This is evident even during one season; for example, amplitudes of modes <I>f</I><SUB>8</SUB> and <I>f</I><SUB>C</SUB> were found to change by a factor of 2–3 within about 50 d during 2005.</P><P>We use a small grid of models to constrain the main mode (<I>f</I><SUB>1</SUB>), which most likely represents the radial fundamental pulsation. The groups of <I>p</I>-mode frequencies appear to lie in the vicinity of the consecutive radial overtones, up to the third one. Despite the large number of <I>g</I>-mode frequencies observed, we failed to identify them, most likely because of the disruption of asymptotic behaviour by mode trapping. The observed frequencies were not, however, fully exploited in terms of seismic analysis which should be done in the future with a larger grid of reliable evolutionary models of hot subdwarfs.</P>

Final report of the pilot study CCQM-P110-B1: A comparison of nitrogen dioxide (NO₂) in nitrogen standards at 10 µmol/mol by Fourier transform infrared spectroscopy (FT-IR)

Flores, Edgar,Idrees, Faraz,Moussay, Philippe,Viallon, Joë,le,Wielgosz, Robert,Ferná,ndez, Teresa,Rojo, André,s,Ram&iacute,rez, Sergio,Aoki, Nobuyuki,Kato, Kenji,Jeongsoon, Lee,Moon, D Springer-Verlag 2012 METROLOGIA -BERLIN- Vol.49 No.-

<P>This pilot study compares the performance of participants in analyzing gas mixtures of nitrogen dioxide in nitrogen by comparison with in-house gravimetric standards using Fourier transformed infrared spectroscopy (FT-IR). In this study the same gas mixtures were used as in the key comparison CCQM-K74, which was designed to evaluate the level of comparability of National Metrology Institutes' measurement capabilities for nitrogen dioxide (NO<SUB>2</SUB>) at a nominal mole fraction of 10 µmol/mol. In the comparison CCQM-K74 most of the participants used chemiluminescence, with a small number using UV absorption or FT-IR spectroscopy, and thus it is of interest to improve understanding of the comparative performance of these techniques because they do not exhibit any cross-sensitivity to nitric acid (HNO<SUB>3</SUB>), which was known to be present in the mixtures used for the comparison.</P><P>The results of this pilot study indicate good consistency and a level of agreement similar to that reported in the comparison CCQM-K74, demonstrating that FT-IR can be operated as a comparison method when calibrated with appropriate gas standards and can achieve similar measurement uncertainties to chemiluminescence and UV absorption techniques.</P><P>An additional pilot study, CCQM-P110-B2, was conducted on the same gas mixtures in parallel with this pilot study. The second study addressed FT-IR spectroscopy when used to measure the gas mixtures with respect to reference spectra. The results of this second study will be reported elsewhere.</P><P>Main text.To reach the main text of this paper, click on Final Report.</P><P>The final report has been peer-reviewed and approved for publication by the CCQM-GAWG.</P>

Shell evolution of <i>N</i> = 40 isotones towards ⁶⁰Ca: First spectroscopy of ⁶²Ti

Corté,s, M.L.,Rodriguez, W.,Doornenbal, P.,Obertelli, A.,Holt, J.D.,Lenzi, S.M.,Mené,ndez, J.,Nowacki, F.,Ogata, K.,Poves, A.,Rodr&iacute,guez, T.R.,Schwenk, A.,Simonis, J.,Stroberg, S.R. North-Holland Pub. Co 2020 Physics letters. Section B Vol.800 No.-

<P><B>Abstract</B></P> <P>Excited states in the N = 40 isotone <SUP>62</SUP>Ti were populated via the <SUP>63</SUP>V ( p , 2 p ) <SUP>62</SUP>Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using <I>γ</I>-ray spectroscopy. The energies of the 2 1 + → 0 gs + and 4 1 + → 2 1 + transitions, observed here for the first time, indicate a deformed <SUP>62</SUP>Ti ground state. These energies are increased compared to the neighboring <SUP>64</SUP>Cr and <SUP>66</SUP>Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings. The shell-model calculations for <SUP>62</SUP>Ti show a dominant configuration with four neutrons excited across the N = 40 gap. Likewise, they indicate that the N = 40 island of inversion extends down to Z = 20 , disfavoring a possible doubly magic character of the elusive <SUP>60</SUP>Ca.</P>