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

Rodrí,guez, E.,Garcí,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>

A pH/Temperature-Sensitive s-IPN Based on Poly(vinyl alcohol), Poly(vinyl methyl ether-alt-maleic acid) and Poly(vinyl methyl ether) Prepared by Autoclaving

Karla F. García-Verdugo,Andya J. Ramírez-Irigoyen,Mónica Castillo-Ortega,Dora E. Rodríguez-Félix,Jesús M. Quiroz-Castillo,Judith Tánori-Córdova,Francisco Rodríguez-Félix,Antonio Ledezma-Pérez,Teresa d 한국고분자학회 2022 Macromolecular Research Vol.30 No.6

A novel semi-interpenetrating polymer network (s-IPN) based on the entrapment of a thermosensitive polymer, the poly(vinyl methyl ether) (PVME), within a crosslinked 3D structure of poly(vinyl alcohol) (PVA) and poly(vinyl methyl etheralt- maleic acid) (COP) was synthesized by an autoclaving process. The preparation method avoids the use of toxic crosslinkers and allows the simultaneous sterilization of material. The PVA/COP/PVME hydrogel were characterized by Fourier transform infrared spectroscopy, thermal techniques, swelling kinetic measurements, scanning electron microscopy, and rheological analysis. The entrapment of PVME within the hydrated polymer framework significantly modified its transition temperature at pH 7.4 and pH 3 conditions. The swelling kinetics of the s-IPN were dependent on pH (7.4, 3 and 1), and temperature (25 and 37℃). The interpenetrated polymer chains reduced the internal pore sizes of crosslinked network without altering its elastic, solid-like behavior. The loading and in vitro release of 5-fluorouracil, a chemotherapeutic agent, from hydrogel systems were studied at different temperature and pH values. The hydrogels showed a sustained drug release up to 5 h at 37℃, in different pH media. The s-IPN exhibited a promising performance for a range of biomedical applications, in particular, for the controlled drug delivery in response to the pH and temperature conditions.

Pressure-assisted combustion synthesis of red-emitting SrIn₂O₄: Eu3+ phosphor powders for applications in solid state white lamps

C.E. Rodríguez-García,N. Perea-López,S.P. DenBaars,G.A. Hirata 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.5

Red-emitting phosphor powders of SrIn2O4 activated with Eu3+ ions were synthesized by a high pressure assisted combustion method. X-ray diffraction analysis of the crystalline properties of these powders revealed single phase SrIn2O4 for Eu concentrations up to 4 atomic % of Eu. The photo and cathodoluminescence emission spectra of SrIn2O4: Eu3+ powder shows bright red emission mainly caused by the 5D0→7F2 intra-shell transition of Eu3+. Furthermore, photoluminescence excitation (PLE) spectroscopy revealed that an efficient energy transfer from the SrIn2O4 host lattice onto the Eu ions is accomplished in addition to the excitation band peaked at λ = 396 nm that directly excites the Eu ions, making this material an excellent candidate for applications in solid state white-emitting lamps. Red-emitting phosphor powders of SrIn2O4 activated with Eu3+ ions were synthesized by a high pressure assisted combustion method. X-ray diffraction analysis of the crystalline properties of these powders revealed single phase SrIn2O4 for Eu concentrations up to 4 atomic % of Eu. The photo and cathodoluminescence emission spectra of SrIn2O4: Eu3+ powder shows bright red emission mainly caused by the 5D0→7F2 intra-shell transition of Eu3+. Furthermore, photoluminescence excitation (PLE) spectroscopy revealed that an efficient energy transfer from the SrIn2O4 host lattice onto the Eu ions is accomplished in addition to the excitation band peaked at λ = 396 nm that directly excites the Eu ions, making this material an excellent candidate for applications in solid state white-emitting lamps.

Physical Properties of the Sr4Al6O12SO4 Ceramic Compound

J.A. Rodríguez-García,E. Rocha-Rangel,J. López Hernández,C.A. Hernández Bocanegra,A.L. Leal Cruz,J.M. Almanza Robles,J. Torres Torres 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.11

The Sr4Al6O12SO4 ceramic compound was synthesized by a solid state reaction starting from stoichiometric mixtures of 3 : 3 : 1 molar ratio of reactive grade of SrCO3, Al2O3 and SrSO4, respectively. Cylindrical samples were confirmed by uniaxial pressing at 100 MPa and were heat treated at 1400 oC during 4 hrs. Subsequently, the samples were ground and re-conformed in cylindrical shape samples by uniaxial pressing at 300 MPa. The new samples were heat treated at 1400 oC during 24 hrs. This process was done in order to increase density of the samples. The Sr4Al6O12SO4 ceramic compound was characterized by the study of its physical properties such as: density, micro-hardness, thermal expansion and stability, enthalpy of formation, magnetic properties and electrical conductivity. Experimental results show that the maximum density obtained for the Sr4Al6O12SO4 ceramic compound was 2.913 grcm−3, with thermal expansion coefficient of 10.12E−06(oC−1); it also presents an enthalpy of 2.3 KJmol-1 and an excellent thermal stability at elevated temperatures in different atmospheres. In addition, the Sr4Al6O12SO4 ceramic compound is neither electrically conductive nor magnetic.

Competition/antagonism associations of biofilm formation among Staphylococcus epidermidis Agr groups I, II, and III

Sergio Martínez-García,César I. Ortiz-García,Marisa Cruz-Aguilar,Juan Carlos Zenteno,José Martin Murrieta-Coxca,Sonia Mayra Pérez-Tapia,Sandra Rodríguez-Martínez,Mario E. Cancino-Diaz,Juan C. Cancino- 한국미생물학회 2019 The journal of microbiology Vol.57 No.2

Staphylococci have quorum-sensing (QS) systems that enable cell-to-cell communication, as well as the regulation of numerous colonization and virulence factors. The accessory gene regulator (Agr) operon is one of the Staphylococcus genus QS systems. Three groups (I, II, and III) are present in Staphylococcus epidermidis Agr operon. To date, it is unknown whether Agr groups can interact symbiotically during biofilm development. This study analyzed a symbiotic association among Agr groups during biofilm formation in clinical and commensal isolates. Different combinations among Agr group isolates was used to study biofilm formation in vitro and in vivo (using a mouse catheter-infection model). The analysis of Agr groups were also performed from samples of human skin (head, armpits, and nostrils). Different predominant coexistence was found within biofilms, suggesting symbiosis type. In vitro, Agr I had a competition with Agr II and Agr III. Agr II had a competition with Agr III, and Agr II was an antagonist to Agr I and III when the three strains were combined. In vivo, Agr II had a competition to Agr I, but Agr I and II were antagonists to Agr III. The associations found in vitro and in vivo were also found in different sites of the skin. Besides, other associations were observed: Agr III antagonized Agr I and II, and Agr III competed with Agr I and Agr II. These results suggest that, in S. epidermidis, a symbiotic association of competition and antagonism occurs among different Agr groups during biofilm formation.