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.

The medium-term consequences of COVID-19 lockdown on lifestyle among Spanish older people with hypertension, pulmonary, cardiovascular, and musculoskeletal-diseases, depression, and cancer

Rodríguez-Gómez Irene,Sánchez-Martín Coral,García-García Francisco J.,García-Esquinas Esther,Miret Marta,Vicente-Rodriguez Germán,Gusi Narcís,Mañas Asier,Carnicero José A.,Gonzalez-Gross Marcela,Ayuso 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: This study investigated the associations of chronic diseases with changes in lifestyle and health behaviours in older people following the coronavirus disease 2019 (COVID-19) lockdown in Spain and compared the differences in changes over time. METHODS: 1,092 participants (80.3± 5.6 years; 66.5% female) from 2 Spanish cohorts were included. Telephone-based questionnaires were conducted to evaluate lifestyle and health risk behaviours at the end of lockdown and 7 months post-lockdown. Participants were classified as having physician-diagnosed chronic diseases based on self-reported data. Cox proportional models adjusted for major confounders were used. RESULTS: Compared to those without the corresponding chronic diseases, older people with hypertension were less likely to report increased alcohol consumption (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.55 to 0.99). Pulmonary diseases were associated with lower risks of increased sedentary time (HR, 0.58; 95% CI, 0.39 to 0.86) and worsened sleep quality (HR, 0.56; 95% CI, 0.36 to 0.87), while cardiovascular diseases were associated with a lower risk of decreased sedentary time (HR, 0.58; 95% CI, 0.38 to 0.88). Depression was linked to a higher likelihood of improved diet quality (HR, 1.53; 95% CI, 1.00 to 2.36). Cancer pacients were less likely to have worsened sleep quality (HR, 0.44; 95% CI, 0.22 to 0.89) but more likely to have reduced their frequency of social contact (HR, 2.05; 95% CI, 1.05 to 3.99). CONCLUSIONS: Older people with chronic diseases showed beneficial changes in lifestyle and health risk behaviours after the COVID-19 lockdown. In particular, older people with hypertension, pulmonary disease, and cancer tended to make beneficial lifestyle and health behaviour changes. However, older people with cardiovascular disease and depression engaged in more health risk behaviours.

Effect of dopants on the structure of titanium oxide used as a photocatalyst for the removal of emergent contaminants

A. Gil,A.M. García,M. Fernández,M.A. Vicente,B. González-Rodríguez,V. Rives,S.A. Korili 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

Photocatalysts composed of titanium dioxide modified with B, F, N and P have been synthesized, characterized and applied to the degradation of caffeine, diclofenac, ibuprofen and salicylic acid. The modified TiO2 samples were prepared by the sol–gel technique starting from titanium(IV) isopropoxide and using H3BO3, NH4F, N(C2H5OH)3 and H3PO4 as precursors of the modifiers, with the content varying between 0 and 5 wt%. Structural characterization was based on nitrogen physisorption at 196 C, powder X-ray diffraction (PXRD), simultaneous thermogravimetric/differential thermal analysis (TG/ DTA) and X-ray photoelectron spectroscopy (XPS). The structural properties of the modified TiO2 solids were significantly different depending on the nature and amount of modifiers and the calcination temperature. TiO2 in the anatase phase was obtained in all cases and was stable upon calcination at 400 C. The photocatalytic degradation of caffeine, diclofenac, ibuprofen and salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 25 C. The photocatalytic degradation behavior followed the order: caffeine > diclofenac = ibuprofen > salicylic acid. B-doped TiO2 was the most efficient catalyst in the degradation of these selected emerging contaminants.

Systemic Inflammatory Load in Young and Old Ringdoves Is Modulated by Consumption of a Jerte Valley Cherry-Based Product

Jonathan Delgado,María del Pilar Terrón,María Garrido,Carmen Barriga,Sergio Damián Paredes,Javier Espino,Beatriz Rodríguez 한국식품영양과학회 2012 Journal of medicinal food Vol.15 No.8

A chronic subclinical inflammatory status that coexists with immune dysfunction is commonly found in the elderly population. Consumption of foods rich in antioxidants (e.g., cherries) is an attractive strategy to reduce risk from chronic diseases. Based on previous studies showing the antioxidant effect of a Jerte Valley cherry derivative product in humans, the objective of this work was to evaluate the effect of the intake of a Jerte Valley cherry-based beverage on inflammatory load in both young and old ringdoves (Streptopelia risoria). To this purpose, circulating levels of proinflammatory and anti-inflammatory cytokines as well as serum levels of different acute-phase proteins were measured before and after a 10-day treatment with the Jerte Valley cherry-based beverage. Thus, the 10-day treatment with the cherry-based beverage modulated the balance of pro- and anti-inflammatory cytokines in both young and old ringdoves by down-regulating the levels of pro-inflammatory cytokines (interleukin [IL]-1b, tumor necrosis factor-a, and interferon-c) and up-regulating the levels of anti-inflammatory cytokines (IL-4, IL-2, and IL-10). Moreover, the 10-day treatment with the Jerte Valley cherrybased product reduced the levels of several proteins involved in acute-phase responses, such as C-reactive protein, haptoglobin,a2-macroglobulin, and serum amyloid P component. On the other hand, old birds showed imbalanced levels of inflammatory markers toward a pro-inflammatory status, thereby underlining the fact that aging is usually accompanied by systemic inflammation and inflammation-related chronic diseases. To sum up, the data suggest a potential health benefit by consuming the cherry-based beverage, especially in aged populations, through their anti-inflammatory properties.

A general exergy-based environmental impact index

Sósimo E. Díaz-Méndez,José María Rodríguez-Lelis,Abel Hernández-Guerrero 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

An ecosystem is a complex system in which biotic and abiotic factors interact and influence each other both directly and indirectly. Each of these factors has to comply with a specific function in the different processes that occur inside the ecosystem, whether transporting or transforming energy or both. When anthropogenic emissions are produced, part of the useful energy of the ecosystem is used to assimilate or absorb those emissions, and the energy spent, loses its function and becomes lost work in accordance with the Gouy-Stodola theorem. Thus, the work that an ecosystem can carry out varies as a function of the lost work produced by anthropogenic sources. The permanency or loss of the ecosystem depends on how many irreversibilities it can support. The second law of thermodynamics through a systematic use of the exergy and lost work is the basis of this paper where a general environmental impact index, based on exergy, is proposed. For the purpose of this work, the ecosystem is divided in subsystems--water, soil, atmosphere, organisms and society--all of them inter-related. The ideal work variation can be obtained from each subsystem within the selected ecosystem, and a global index can be determined by adding the partial lost work of each subsystem. This global index is then used to determine the trend followed by the ecosystem from its pristine, original or environmental line base state. This environmental impact index applicability is presented for a simple combustion example.

<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 novel approach for the rigid body guidance synthesis of planar RRPR linkages

Selma J. Rodríguez-González,Henry A. Suárez-Velásquez,J. Jesús Cervantes-Sánchez,José M. Rico-Martínez 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

This paper demonstrates that the maximum number of poses that can be exactly reached by a planar RRPR linkage is four, while the design for five poses requires the relaxation of displacement constraints at one prescribed pose. To this end, a novel and explicit condition for the synthesis of RP dyads with five prescribed poses is correspondingly introduced. It leads to a new and efficient approach to synthesize planar RRPR linkages, which is equipped with a branching identification procedure. Two successful case studies are provided to validate the applicability of the proposed synthesis approach.

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.

Development of the braconid wasp Cotesia flavipes in two Crambids, Diatraea saccharalis and Eoreuma loftini: Evidence of host developmental disruption

A.M.A. Mahmoud,E.J. De Luna-Santillana,X. Guo,F. Reyes-Villanueva,Mario A. Rodríguez-Pérez 한국응용곤충학회 2012 Journal of Asia-Pacific Entomology Vol.15 No.1

Cotesia flavipes is an important gregarious larval endoparasitoid of several crambid stem borers, including Diatraea saccharalis. The suitability of two crambid species, Eoreuma loftini and D. saccharalis, pests of sugarcane and rice in Texas, for C. flavipes development was tested. The effect of parasitization by C. flavipes on encapsulation response was assessed in vivo in both D. saccharalis and E. loftini. The results indicated that the parasitoid developed and emerged successfully in D. saccharalis larvae. Although E. loftini larvae were readily parasitized by C. flavipes parasitoids, no wasp larvae hatched from the eggs in this host because eggs were encapsulated by the host's hemocytes. The developmental fate of the E. loftini larvae with encapsulated parasitoids was variable. Most died as abnormal fifth instars or as post-wandering prepupae, while a few developed normally to the pupal stage. In vivo experiments, there was a significant reduction in the percent of beads encapsulated in parasitized larvae in both hosts. However, the percent of beads showing melanization decreased significantly in parasitized D. saccharalis larvae but did not differ significantly in parasitized or unparasitized E. loftini larvae. Our results showed that D. saccharalis is a suitable host for C. flavipes whereas E. loftini is an unsuitable host. This study indicated that lepidopteran stem borers that are taxonomically,behaviorally, and ecologically very similar can differ in their ability to encapsulate a parasitoid species.

Synthesis by a solid state reaction of the Sr4Al6O12SO4 compound

J.A. Rodríguez-García,E. Rocha-Rangel,J. Torres-Torres,J. M. Almanza-Robles 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.3

The synthesis and formation of Sr4Al6O12SO4 in the system SrCO3-Al2O3-SrSO4 has been studied in the range of temperatures from 800 oC to 1400 oC using X-ray diffraction, thermo gravimetric, differential thermal and scanning electron microscopy analysis. Pellets of a mixture of 3 : 3 : 1 molar ratio of reactive grade Al2O3, SrCO3 and SrSO4 respectively were prepared, by solid state sintering, the reactive powders were thoroughly mixed under high energy ball-milling, uniaxially pressed into cylindrical samples and pressureless-sintered. Additionally the densities of some samples that were heat treated for 10 h at 1200, 1300 and 1400 oC were determined by the Archimedes method. The powder mixture was analyzed by TGA and DTA from room temperature to 1200 oC. XRD patterns indicated the formation of Sr3Al2O6 and SrAl2O4 as intermediate phases that nearly at the end of the process reacted with SrSO4 to form Sr4Al6O12SO4. The formation of Sr4Al6O12SO4 was complete at 1150 oC as XRD and DTA analysis indicated. An increase in the heat treatment time promotes the formation of Sr4Al6O12SO4at lower temperatures. The Sr4Al6O12SO4 powders were composed of spherical particles of small agglomerates. Results of density measurement indicated that only 80% of the theoretical density was reached for a treatment at 1400 oC of 10 h, which indicated the difficulty to obtain a dense material.