Thermal shock resistance of mullite/Sr-celsian/zirconia composites

Rodríguez-Salazar P.,Almanza-Robles J. M.,Cortés-Hernández D. A.,Escobedo-Bocardo J. C. 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.6

The thermal shock resistance of novel mullite /Sr-celsian /zirconia composites was studied. The eff ect of the Sr-celsian (15, 20, 25 wt.%) and ZrO 2 (5, 15, 25 wt.%) amounts on the thermal shock resistance, was evaluated. The composites were obtained at 1450 °C. Thermal shock resistance was performed by heating samples up to a selected temperature (∆ T = 200–1000 °C) and then suddenly immersed in water. After testing, the bending strength was evaluated and the results were statistically analyzed using Minitab with a confi dence level of 0.05. Pareto charts showed that Sr-celsian and zirconia content have the highest infl uence on fl exural strength after thermal shock. The highest thermal shock resistance was obtained for the composites with the highest amount of zirconia and Sr-celsian. Most of the composites showed a decrease in strength of around 75%. The strength of the composites with 20 or 25 wt.% of celsian and 25 wt.% zirconia increased at ∆ T of 1000 °C. The Pareto chart for these composites showed that zirconia has the highest eff ect on strength. A change in expansion is shown between 800 and 900 °C, indicating the transformation of monoclinic to tetragonal zirconia. This transformation generates microc- racks that defl ect cracks generated during thermal stress. Also, residual stresses are generated during cooling which plays a role in absorbing the energy of a generated crack. The strontium celsian forms an interlocked microstructure that improves strength. These composites are promising materials for applications in which sudden and extreme temperature changes occur.

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.

<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>

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.

Short-, Intermediate-, and Long-Term Changes in Basophil Reactivity Induced by Venom Immunotherapy

Ana Rodríguez Trabado,Carmen Cámara Hijón,Alfonso Ramos Cantariño,Silvia Romero-Chala,José Antonio García-Trujillo,Luis Miguel Fernández Pereira 대한천식알레르기학회 2016 Allergy, Asthma & Immunology Research Vol.8 No.5

Purpose: The basophil activation test (BAT) has been used to monitor venom immunotherapy (VIT) due to its high specificity. A previous study has reported a good correlation between a significant decrease in basophil activation during 5 years of VIT and clinical protection assessed by sting challenge. The following prospective study was performed to examine changes in basophil reactivity over a complete VIT period of 5 years. Methods: BAT in a dose-response curve was studied prospectively in 10 hymenoptera venom-allergic patients over 5 years of VIT. BAT was performed at the time of diagnosis, 1 month after finishing the VIT build-up phase, and 3, 6, 12, 24, and 60 months after beginning treatment. The repeated measures ANOVA was applied to evaluate basophil activation changes throughout VIT. A cross-sectional study was also performed in 6 patients who received treatment for more than 3 years, and in another 12 patients who followed immunotherapy for at least 5 years. Results: An early activation decrease was observed during the first 3 months of treatment, compared to pre-treatment values. This activation decrease was not maintained 6 to 18 months after treatment, but was observed again after 2 years of treatment, and maintained until the completion of the 5-year immunotherapy period. In cross-sectional analysis, the 6 patients who received treatment for 3 years, and 9 of the 12 patients who received treatment for 5 years, had negative BAT results. Three patients in this last group had positive BAT results and 2 patients had systemic reactions after field stings. Conclusions: BAT appears to be an optimal non-invasive test for close monitoring of VIT.

Internal maxillary artery (IMax) – middle cerebral artery bypass in a patient with bilateral atherosclerotic carotid occlusion: A technical case report

Javier Degollado-García,Martin R. Casas-Martínez,Bill Roy Ferrufino Mejia,Juan C. Balcázar-Padrón,Héctor A. Rodríguez-Rubio,Edgar Nathal 대한뇌혈관외과학회 2024 Journal of Cerebrovascular and Endovascular Neuros Vol.26 No.1

Since the first description of the possible utilization of the internal maxillary artery for bypass surgery, there are some reports of its use in aneurysm cases; however, there is no information about the possible advantages of this type of bypass for cerebral ischemic disease.We present a 77-year-old man with a history of diabetes, hypertension, systemic atherosclerosis, and two acute myocardial infarctions with left hemiparesis. Imaging studies reported total occlusion of the right internal carotid artery and 75% occlusion on the left side, with an old opercular infarction and repeated transient ischemic attacks in the right middle cerebral artery territory despite medical treatment. After a consensus, we decided to perform a bypass from the internal maxillary artery to the M2 segment of the middle cerebral artery using a radial artery graft. After performing the proximal anastomosis, the calculated graft’s free flow was 216 ml/min. Subsequently, after completing the bypass, the patency was confirmed with fluorescein videoangiography and intraoperative Doppler. Postoperatively, imaging studies showed improvement in the perfusion values and the hemiparesis from 3/5 to 4+/5. The patient was discharged one week after the operation, with a modified Rankin scale of 1, without added deficits.The use of revascularization techniques in steno-occlusive disease indicates a select group of patients that may benefit from this procedure. In addition, internal maxillary artery bypass has provided a safe option for large areas of ischemia that cannot be supplied with a superficial temporal artery - middle cerebral artery bypass.

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.

Dye-Perfused Human Placenta for Simulation in a Microsurgery Laboratory for Plastic Surgeons

Zambrano-Jerez Laura C.,Díaz-Santamaría Karen D.,Rodríguez-Santos María A.,Alarcón-Ariza Diego F.,Meléndez-Flórez Genny L.,Ramírez-Blanco Mónica A. 대한성형외과학회 2023 Archives of Plastic Surgery Vol.50 No.6

In recent decades, a number of simulation models for microsurgical training have been published. The human placenta has received extensive validation in microneurosurgery and is a useful instrument to facilitate learning in microvascular repair techniques as an alternative to using live animals. This study uses a straightforward, step-by-step procedure for instructing the creation of simulators with dynamic flow to characterize the placental vascular tree and assess its relevance for plastic surgery departments. Measurements of the placental vasculature and morphological characterization of 18 placentas were made. After the model was used in a basic microsurgery training laboratory session, a survey was given to nine plastic surgery residents, two microsurgeons, and one hand surgeon. In all divisions, venous diameters were larger than arterial diameters, with minimum diameters of 0.8 and 0.6 mm, respectively. The majority of the participants considered that the model faithfully reproduces a real microsurgical scenario; the consistency of the vessels and their dissection are similar in in vivo tissue. Furthermore, all the participants considered that this model could improve their surgical technique and would propose it for microsurgical training. As some of the model's disadvantages, an abundantly thick adventitia, a thin tunica media, and higher adherence to the underlying tissue were identified. The color-perfused placenta is an excellent tool for microsurgical training in plastic surgery. It can faithfully reproduce a microsurgical scenario, offering an abundance of vasculature with varying sizes similar to tissue in vivo, enhancing technical proficiency, and lowering patient error.

Adhesion strength in laminated glazings containing multilayer solar control coatings

J. O. Aguilar,J. M. Rodríguez-Lelis,M. Carrasco de la Fuente,C. López-Mata,J. A. Arellano-Cabrera,F. Chan 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.6

We report on the mechanical and optical properties exhibited by a five layer laminated glazing (glass/PVB/PET/PVB/glass) in which a 0.1 mm thick polyethylene-terephthalate (PET) sheet carries a 70-110 nm CuS solar control coatings on either one or both sides of it and laminated with 0.38 mm clear polyvinyl-butyral (PVB) sheets in an autoclave at 135°C for 30 min under a pressure, 13 kg/cm2. The CuS coating was obtained by chemical deposition at 28°C during 1 h (70 nm) or 2 h (110 nm). The optical transmittance (T) of these laminated glazing is less than 1% in the ultraviolet region; 17-32% in the visible region, and 4-12% in the infrared region, depending on the CuS film thickness and whether the PET sheet is coated on one or both sides. The specular reflectance (R) of the glazing in the visible region is similar to that of a monolithic glass: about 10%, but in the infrared it increases toward 20%. The mechanical properties were evaluated through a compressive test giving interfacial adhesive strength of the laminated: 1.5-2 MPa for PET with a single side CuS coating and 3.4 MPa for the laminate with a PET coated on both sides.

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.