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>

Asymptotic behavior of grafting rays

Dí,az, Raquel,Kim, Inkang Springer-Verlag 2012 Geometriae dedicata Vol.158 No.1

Tanzawaic acids isolated from a marine-derived fungus of the genus <i>Penicillium</i> with cytotoxic activities

Cardoso-Mart&iacute,nez, Faviola,de la Rosa, José,M.,Dí,az-Marrero, Ana R.,Darias, José,Cerella, Claudia,Diederich, Marc,Cueto, Mercedes The Royal Society of Chemistry 2015 Organic & Biomolecular Chemistry Vol.13 No.26

<P>Tanzawaic acids M (<B>1</B>), N (<B>2</B>), O (<B>3</B>) and P (<B>4</B>) and the known tanzawaic acids B (<B>5</B>) and E (<B>6</B>), have been isolated from an extract of a cultured marine-derived fungus (strain CF07370) identified as a member of the genus <I>Penicillium</I>. The structures of <B>1–4</B> were determined based on spectroscopic evidence. The antimicrobial and cytotoxic activities of compounds <B>1–6</B> were evaluated.</P> <P>Graphic Abstract</P><P>Tanzawaic acids M (<B>1</B>), N (<B>2</B>), O (<B>3</B>) and P (<B>4</B>) were isolated from an extract of a cultured marine-derived fungus (strain CF07370) identified as a member of the genus <I>Penicillium</I>. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5ob00773a'> </P>

Optimal replacement policy under a general failure and repair model: Minimal versus worse than old repair

Badí,a, F.G.,Berrade, M.D.,Cha, Ji Hwan,Lee, Hyunju Elsevier 2018 Reliability engineering & system safety Vol.180 No.-

<P><B>Abstract</B></P> <P>We analyze the optimal replacement policy for a system subject to a general failure and repair model. Failures can be of one of two types: catastrophic or minor. The former leads to the replacement of the system, whereas minor failures are followed by repairs. The novelty of the proposed model is that, after repair, the system recovers the operational state but its condition is worse than that just prior to failure (worse than old). Undertrained operators or low quality spare parts explain this deficient maintenance. The corresponding failure process is based on the Generalized Pólya Process which presents both the minimal repair and the perfect repair as special cases. The system is replaced by a new one after the first catastrophic failure, and also undergoes two sorts of preventive maintenance based on age and after a predetermined number of minor failures whichever comes first. We derive the long-run average cost rate and study the optimal replacement policy. Some numerical examples illustrate the comparison between the as bad-as-old and the worse than old conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A maintenance procedure for worse than old repair is studied. </LI> <LI> A general failure process based on the Generalized Pólya Process is considered. </LI> <LI> Comparison with the minimal repair policy is performed. </LI> </UL> </P>

<i>δ</i> Sct-type pulsations in eclipsing binary systems: Y Cam

Rodr&iacute,guez, E.,Garc&iacute,a, J. M.,Costa, V.,Lampens, P.,van Cauteren, P.,Mkrtichian, D. E.,Olson, E. C.,Amado, P. J.,Daszyń,ska-Daszkiewicz, J.,Turcu, V.,Kim, S.-L.,Zhou, A. Y.,Ló,p Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.408 No.4

<P>ABSTRACT</P><P>We present the results of a three-continent multisite photometric campaign carried out on the Algol-type eclipsing binary system Y Cam, in which the primary component is a multiperiodic δ Sct-type pulsator. The observations consist of 86 nights and more than 450 h of useful data collected mainly during the Northern winter 2002–2003. This means that this is the most extensive time series for such kind of systems obtained so far. These observations were collected mostly in the Johnson V filter, but they also include, for the first time, nearly complete binary light curves in simultaneous Strömgren <I>uvby</I> filters together with a few Crawford Hβ data obtained around the orbital phase of the first quadrature. A detailed photometric analysis is presented for both binarity and pulsation. The results indicate a semidetached system with the secondary filling its Roche lobe. No significant contribution from a third body is found. The residuals from the computed binary solution were then used to investigate the pulsational content of the primary component. The frequency analysis of the out-of-primary-eclipse data leads to a set of eight significant and independent pulsational peaks in a well-defined region of the frequency domain. This means that this is the largest set of excited modes discovered so far in the pulsating component of such kind of systems. The possibility of aliasing problems during the present run or short-term time-scale amplitude variations in some of them was investigated with null results. Indeed the results indicate that <I>f</I><SUB>1</SUB> and <I>f</I><SUB>3</SUB> form a frequency doublet with a beat period of <I>P</I><SUB>beat</SUB>= 17.065 d. Our results confirm the frequencies already detected by earlier authors and show the presence of some additional significant peaks. The observed amplitudes during the present run are also consistent with those derived from older data sets. We perform a preliminary mode identification for most of the frequencies on the basis of the collected multicolour photometry, the observed frequency spacings and the mode visibility in eclipsing binaries.</P>

Assessing estrogen signaling aberrations in breast cancer risk using genetically engineered mouse models.

Furth, Priscilla A,Cabrera, M Carla,Dí,az-Cruz, Edgar S,Millman, Sarah,Nakles, Rebecca E New York Academy of Sciences 2011 Annals of the New York Academy of Sciences Vol.1229 No.1

<P>Aberrations in estrogen signaling increase breast cancer risk. Molecular mechanisms that impact breast cancer initiation, promotion, and progression can be investigated using genetically engineered mouse models. Increasing estrogen receptor alpha (ER관) expression levels twofold is sufficient to initiate and promote breast cancer progression. Initiation and promotion can be increased by p53 haploinsufficiency and by coexpressing the nuclear coactivators amplified in breast cancer 1 (AIB1) or the splice variant AIB1??3. Progression to invasive cancer is found with coexpression of these nuclear coactivators as well as following a single dose of 7,12-dimethylbenz(a)anthracene. Loss of signal transducer and activator of transcription 5a reduces the prevalence of initiation and promotion but does not protect from invasive cancer development. Cyclin D1 loss completely interrupts mammary epithelial proliferation and survival when ER관 is overexpressed. Loss of breast cancer gene 1 increases estrogen signaling and cooperates with ER관 overexpression in initiation, promotion, and progression of mammary cancer.</P>

Multi-site, multi-year monitoring of the oscillating Algol-type eclipsing binary CT Herculis

Lampens, P.,Strigachev, A.,Kim, S.-L.,Rodr&iacute,guez, E.,Ló,pez-Gonzá,lez, M. J.,Vidal-Sa&iacute,nz, J.,Mkrtichian, D.,Koo, J.-R.,Kang, Y. B.,Van Cauteren, P.,Wils, P.,Kraicheva, Z.,Dimi EDP Sciences 2011 Astronomy and astrophysics Vol.534 No.2

<P>We present the results of a multi-site photometric campaign carried out in 2004–2008 for the Algol-type eclipsing binary system CT Her, the primary component of which displays δ Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V, which were analysed using the method of Wilson-Devinney (PHOEBE). After identifying an adequate binary model and removing the best-fit light-curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour. We confirm the presence of rapid pulsations with a main period of 27.2 min. Up to eight significant frequencies with semi-amplitudes in the range 3 to 1 mmag were detected, all of which lie in the frequency range 43.5–53.5 d<SUP>−1</SUP>. This result is independent of the choice of the primary’s effective temperature (8200 or 8700 K) since the light-curve models of the binary are very similar in both cases. This is yet another case of a complex frequency spectrum observed for an accreting δ Scuti-type star (after Y Cam). In addition, we demonstrate that the amplitudes of several pulsation frequencies provide evidence of variability on timescales as short as 1–2 years, perhaps even less. Moreover, our analysis takes into account some recently acquired spectra, from which we obtained the corresponding radial velocities for the years 2007–2009. Investigation of the O–C diagram shows that further monitoring of the epochs of eclipse minima of CT Her will cast new light on the evolution of its orbital period.</P>

Magnetohydrodynamic Oscillations in the Solar Corona and Earth’s Magnetosphere: Towards Consolidated Understanding

Nakariakov, V. M.,Pilipenko, V.,Heilig, B.,Jel&iacute,nek, P.,Karlický,, M.,Klimushkin, D. Y.,Kolotkov, D. Y.,Lee, D. H.,Nisticò,, G.,Doorsselaere, T. D. Reidel Pub. Co 2016 Space science reviews Vol.200 No.1

<P>Magnetohydrodynamic (MHD) oscillatory processes in different plasma systems, such as the corona of the Sun and the Earth's magnetosphere, show interesting similarities and differences, which so far received little attention and remain under-exploited. The successful commissioning within the past ten years of THEMIS, Hinode, STEREO and SDO spacecraft, in combination with matured analysis of data from earlier spacecraft (Wind, SOHO, ACE, Cluster, TRACE and RHESSI) makes it very timely to survey the breadth of observations giving evidence for MHD oscillatory processes in solar and space plasmas, and state-of-the-art theoretical modelling. The paper reviews several important topics, such as Alfv,nic resonances and mode conversion; MHD waveguides, such as the magnetotail, coronal loops, coronal streamers; mechanisms for periodicities produced in energy releases during substorms and solar flares, possibility of Alfv,nic resonators along open field lines; possible drivers of MHD waves; diagnostics of plasmas with MHD waves; interaction of MHD waves with partly-ionised boundaries (ionosphere and chromosphere). The review is mainly oriented to specialists in magnetospheric physics and solar physics, but not familiar with specifics of the adjacent research fields.</P>

The variability of magnetic activity in solar‐type stars

Fabbian, D.,Simoniello, R.,Collet, R.,Criscuoli, S.,Korhonen, H.,Krivova, N. A.,Olá,h, K.,Jouve, L.,Solanki, S. K.,Alvarado‐,Gó,mez, J. D.,Booth, R.,Garc&iacute,a, R. A.,Lehtinen, J. WILEY‐VCH Verlag GmbH Co. KGaA 2017 Astronomische Nachrichten Vol.338 No.7

<P>This article reviews the current knowledge and status of investigations on the variable magnetic activity of cool stars. We discuss the Sun in the context of solar‐type stars, highlighting peculiarities and common features in terms of its magnetic activity and variability over different time scales. We examine how both theory and observations are providing new clues about the main physical processes that generate magnetic fields in the interior of cool stars, as well as about those that lead to evolving stellar surface magnetism and varying chromospheric and coronal phenomena. We then proceed to discuss the relations between stellar age, rotation, and activity throughout the evolution of cool stars. Finally, we touch upon the importance of understanding stellar magnetism also in view of its effect on planetary environments.</P>

Structural characterization of ultrafine-grained interstitial-free steel prepared by severe plastic deformation

Č,&iacute,ž,ek, J.,Janed,ek, M.,Krajň,á,k, T.,Strá,ská,, J.,Hruš,ka, P.,Gubicza, J.,Kim, H.S. Elsevier 2016 Acta materialia Vol.105 No.-

<P>Interstitial free steel with ultrafine-grained (UFG) structure was prepared by high-pressure torsion (HPT). The development of the microstructure as a function of the number of HPT turns was studied at the centre, half-radius and periphery of the HPT-processed disks by X-ray line profile analysis (XLPA), positron annihilation spectroscopy (PAS) and electron microscopy. The dislocation densities and the dislocation cell sizes determined by XLPA were found to be in good agreement with those obtained by PAS. The evolution of the dislocation density, the dislocation cell and grain sizes, the vacancy cluster size, as well as the high-angle grain boundary (HAGB) fraction was determined as a function of the equivalent strain. It was found that first the dislocation density saturated, then the dislocation cell size reached its minimum value and finally the grain size got saturated. For very high strains after the saturation of grain size the HAGB fraction further increased. The PAS investigations revealed that vacancies introduced by severe plastic deformation agglomerated into small clusters consisting of 9-14 vacancies. The evolution of the yield strength calculated from the microhardness as a function of strain was explained by the development of the defect structure. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>