스페인 정치선전에 언어학전 연구 (1977-1986)

Rojas, Eva Gomez,Eva Gomez Rojas 한국외국어대학교 1988 한국외국어대학교 논문집 Vol.21 No.1

Multiferroic effect of multilayer low-distorted doped bismuth ferrite thin films as a function of sputtering power and crystallographic texture

G. Rojas-George,A. Concha-Balderrama,H. Esparza-Ponce,J.J. Gervacio-Arciniega,M.P. Cruz,V. Orozco-Carmona,A. Reyes-Rojas 한국물리학회 2017 Current Applied Physics Vol.17 No.6

Low-distortion rhombohedral multilayer barium-nickel co-doped BiFeO3 (Bi0.75Ba0.25Fe0.975Ni0.025O3) multiferroic thin films were grown on Pt/TiO2/SiO2/Si substrates by reactive RF magnetron sputtering, as a function of sputtering power. X-ray diffraction showed that Bi0.75Ba0.25Fe0.975Ni0.025O3 multilayer films have a pseudocubic-type structure. Piezoresponse force microscopy demonstrated polarization switching in all films at room temperature. Scanning electron microscopy showed different morphologies depending on the sputtering power used during the deposition process and that the thickness of the film decreases from about 142 nm to 72 nm as the sputtering power decreases. Magnetization results showed that as the thickness of the film decreases, the magnetization of the film increases. Thus, there is a direct relation between the sputtering power, thickness and the magnetization of the film. A direct relation between in-plane residual stress and thin film thickness has been obtained. This causes the main axe of the BO6 octahedra to be tilted from 90 to 45 (from thin-film surface) by a texture crystal volume of 29 and 18% in the (012) and (110) crystallographic planes respectively.

NUMERICAL METHOD FOR SINGULARLY PERTURBED THIRD ORDER ORDINARY DIFFERENTIAL EQUATIONS OF REACTION-DIFFUSION TYPE

ROJA, J. CHRISTY,TAMILSELVAN, A. The Korean Society for Computational and Applied M 2017 Journal of applied mathematics & informatics Vol.35 No.3

In this paper, we have proposed a numerical method for Singularly Perturbed Boundary Value Problems (SPBVPs) of reaction-diffusion type of third order Ordinary Differential Equations (ODEs). The SPBVP is reduced into a weakly coupled system of one first order and one second order ODEs, one without the parameter and the other with the parameter ${\varepsilon}$ multiplying the highest derivative subject to suitable initial and boundary conditions, respectively. The numerical method combines boundary value technique, asymptotic expansion approximation, shooting method and finite difference scheme. The weakly coupled system is decoupled by replacing one of the unknowns by its zero-order asymptotic expansion. Finally the present numerical method is applied to the decoupled system. In order to get a numerical solution for the derivative of the solution, the domain is divided into three regions namely two inner regions and one outer region. The Shooting method is applied to two inner regions whereas for the outer region, standard finite difference (FD) scheme is applied. Necessary error estimates are derived for the method. Computational efficiency and accuracy are verified through numerical examples. The method is easy to implement and suitable for parallel computing. The main advantage of this method is that due to decoupling the system, the computation time is very much reduced.

Design of isolated footings of circular form using a new model

Rojas, Arnulfo Luevanos Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4

This paper presents the design of reinforced concrete circular footings subjected to axial load and bending in two directions using a new model. The new model considers the soil real pressure acting on contact surface of the circular footings and these are different, with a linear variation in the contact area, these pressures are presented in terms of the axial load, moments around the axis "X" and the axis "Y". The classical model takes into account only the maximum pressure of the soil for design of footings and it is considered uniform at all points of contact area. Also, a comparison is presented in terms of the materials used (steel and concrete) between the two models shown in table, being greater the classical model with respect the new model. Therefore, the new model is the most appropriate, since it is more economic and also is adjusted to real conditions.

우유 한 컵

Roja, Manuel,유종철 한국외국어대학 학도호국단 1977 외대 Vol.12 No.1

Clinical and Economic Outcomes Associated with Complicated Urinary Tract Infections Caused by Carbapenem-resistant Enterobacterales in Patients Admitted to a Referral Center in Lima, Peru

Rojas-Alvarado Annel,Dioses-Diaz Karim,Sandoval-Ahumada Roxana,Pérez-Lazo Giancarlo 대한감염학회 2025 Infection and Chemotherapy Vol.57 No.3

Background Urinary tract infections (UTIs) affect 150 million people annually, with increased incidence among individuals over 60 years of age. Complicated UTIs (cUTIs), frequently caused by multidrug-resistant pathogens such as Escherichia coli and Klebsiella pneumoniae, present therapeutic challenges due to host factors and anatomical abnormalities. Carbapenem-resistant Enterobacterales (CRE) infections are of particular concern as they are associated with higher mortality and healthcare costs. This study aimed to compare the clinical and economic outcomes of cUTIs caused by CRE and carbapenem-susceptible Enterobacterales (CSE) at a referral hospital in Lima, Peru. Materials and Methods This retrospective cohort study included 200 patients with cUTI admitted to the emergency department. Patients were categorized into two groups: those with CRE-cUTI and those with CSE-cUTI. Data were collected from electronic medical records, including demographics, comorbidities, antimicrobial treatments, and clinical outcomes, with a primary focus on the 30-day mortality. Kaplan-Meier survival curves, log-rank tests, and generalized linear models were used to assess mortality risk factors. Adjusted relative risks (aRRs) were reported with 95% confidence intervals (CI). The final multivariate model was adjusted for three variables selected based on epidemiological relevance: carbapenem resistance, septic shock on admission, and Charlson comorbidity index. Hospitalization costs were calculated based on the hospital’s fee schedule, whereas antibiotic costs were estimated by multiplying the unit cost of each antimicrobial by the total number of vials used for cUTI treatment. Results Twenty-one patients with CRE-cUTI and 179 with CSE-cUTI were enrolled. Third-generation cephalosporins and carbapenems were the most frequently used empirical antibiotics. Inappropriate empirical therapy was higher in the CRE group (76.2% vs. 51.4%, P=0.031). Among the CRE isolates, blaNDM,blaKPC, and blaOXA-48 were identified. The targeted therapies included amikacin and colistin. The 30-day mortality rate was significantly higher in the CRE group than in the CSE group (38.1% vs. 11.7%, P=0.004). Multivariate analysis revealed that an increased Charlson comorbidity index (aRR 1.18; 95% CI, 1.08–1.30; P<0.001), septic shock on admission (aRR 3.57, 95% CI, 1.85-6.88; P<0.001), and CRE infection (aRR 2.19, 95% CI, 1.16–4.16; P=0.015) were significant predictors of mortality. Hospital stay costs were also higher in the CRE group ($4691.6 vs. $2920.9; P=0.032). Conclusion Patients with cUTI caused by CRE experienced significantly higher 30-day mortality and hospital costs than those with cUTI caused by CSE. Effective prevention and management strategies are crucial to improve outcomes and reduce the economic burden of CRE-cUTIs. Background Urinary tract infections (UTIs) affect 150 million people annually, with increased incidence among individuals over 60 years of age. Complicated UTIs (cUTIs), frequently caused by multidrug-resistant pathogens such as Escherichia coli and Klebsiella pneumoniae, present therapeutic challenges due to host factors and anatomical abnormalities. Carbapenem-resistant Enterobacterales (CRE) infections are of particular concern as they are associated with higher mortality and healthcare costs. This study aimed to compare the clinical and economic outcomes of cUTIs caused by CRE and carbapenem-susceptible Enterobacterales (CSE) at a referral hospital in Lima, Peru. Materials and Methods This retrospective cohort study included 200 patients with cUTI admitted to the emergency department. Patients were categorized into two groups: those with CRE-cUTI and those with CSE-cUTI. Data were collected from electronic medical records, including demographics, comorbidities, antimicrobial treatments, and clinical outcomes, with a primary focus on the 30-day mortality. Kaplan-Meier survival curves, log-rank tests, and generalized linear models were used to assess mortality risk factors. Adjusted relative risks (aRRs) were reported with 95% confidence intervals (CI). The final multivariate model was adjusted for three variables selected based on epidemiological relevance: carbapenem resistance, septic shock on admission, and Charlson comorbidity index. Hospitalization costs were calculated based on the hospital’s fee schedule, whereas antibiotic costs were estimated by multiplying the unit cost of each antimicrobial by the total number of vials used for cUTI treatment. Results Twenty-one patients with CRE-cUTI and 179 with CSE-cUTI were enrolled. Third-generation cephalosporins and carbapenems were the most frequently used empirical antibiotics. Inappropriate empirical therapy was higher in the CRE group (76.2% vs. 51.4%, P=0.031). Among the CRE isolates, blaNDM,blaKPC, and blaOXA-48 were identified. The targeted therapies included amikacin and colistin. The 30-day mortality rate was significantly higher in the CRE group than in the CSE group (38.1% vs. 11.7%, P=0.004). Multivariate analysis revealed that an increased Charlson comorbidity index (aRR 1.18; 95% CI, 1.08–1.30; P<0.001), septic shock on admission (aRR 3.57, 95% CI, 1.85-6.88; P<0.001), and CRE infection (aRR 2.19, 95% CI, 1.16–4.16; P=0.015) were significant predictors of mortality. Hospital stay costs were also higher in the CRE group ($4691.6 vs. $2920.9; P=0.032). Conclusion Patients with cUTI caused by CRE experienced significantly higher 30-day mortality and hospital costs than those with cUTI caused by CSE. Effective prevention and management strategies are crucial to improve outcomes and reduce the economic burden of CRE-cUTIs.

[ $G_{\delta}$ ]-CONNECTEDNESS AND $G_{\delta}$-DISCONNECTEDNESS IN FUZZY BITOPOLOGICAL SPACES

Roja, E.,Uma, M.K.,Balasubramanian, G. The Youngnam Mathematical Society Korea 2007 East Asian mathematical journal Vol.23 No.2

In this paper, the concepts of pairwise fuzzy $G_{\delta}$-connected spaces and pairwise fuzzy $G_{\delta}$-extremally disconnected spaces are introduced. The concept of pairwise fuzzy $G_{\delta}$-basically disconnected spaces is defined. Characterizations of the above spaces are given besides giving several examples. Interrelations among the spaces introduced are discussed and some relevant counter examples are given.

Zeolite Synthesis in FluorideMedia: Structure Directiontoward ITW by Small Methylimidazolium Cations

Rojas, Alex,Martí,nez-Morales, Evangelina,Zicovich-Wilson, Claudio M.,Camblor, Miguel A. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.4

<P>Pure silica ITW zeolite can be synthesized using 1,2,3-trimethylimidazoliumand 1,3-dimethylimidazolium cations and fluoride anions as structure-directingagents (SDAs). Similarly to the previously reported 1,3,4-trimethylimidazolium,the dimethyl cation can also produce the zeolite TON, but this higherframework density phase finally transforms <I>in situ</I> into ITW. The structures of the as-made and calcined phases preparedwith the new cations show a unit cell doubling along <I>z</I>, and the refined structures are reported. Periodic Density FunctionalTheory calculations provide the energies of the six SDA-ITW and SDA-TONzeolites, and their relative stabilities fully agree with the experimentalobservations. Structure-direction in this system is discussed fromexperimental and theoretical results that give strong support to theidea that strained silica frameworks are made possible in fluoridemedia by decreasing the covalent character of the Si–O bond.This decreased covalency is enhanced with the 1,2,3-trimethyl isomer,which is shown to be the strongest SDA for ITW and, at the same time,is the more hydrophilic of the three SDAs tested. Our observationswith the three SDAs agree with the so-called Villaescusa’srule, i.e., the low framework density phase is favored at higher concentrations,but at the same time question the supersaturation hypothesis thathas been proposed to explain this rule, since here the low-densityphase is the most stable one.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-4/ja209832y/production/images/medium/ja-2011-09832y_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja209832y'>ACS Electronic Supporting Info</A></P>

Acute and Repeated 28-Day Oral Dose Toxicity Studies of Thymus vulgaris L. Essential Oil in Rats

Rojas-Armas, Juan,Arroyo-Acevedo, Jorge,Ortiz-Sanchez, Manuel,Palomino-Pacheco, Miriam,Castro-Luna, Americo,Ramos-Cevallos, Norma,Justil-Guerrero, Hugo,Hilario-Vargas, Julio,Herrera-Calderon, Oscar Korean Society of ToxicologyKorea Environmental Mu 2019 Toxicological Research Vol.35 No.3

Thymus vulgaris L. is widely used as an ingredient in cooking and in herbal medicine. However, there is little information about its toxicity. The present study was performed to evaluate the acute and repeated 28-day oral dose toxicity of thyme essential oil in rats. For the acute toxicity test, two groups of three rats were used. The rats received a single dose of essential oil: 300 or 2,000 mg/kg of body weight (bw). The rats were observed individually during the first four hours, and then daily until day 14. For the toxicity test with repeated doses, four groups of 10 rats were used. Doses of 100, 250, and 500 mg/kg/day were tested for 28 days. At the end of the experiment, blood was collected and the animals were sacrificed. Histopathological examination showed that in the lungs of rats given the 2,000 mg/kg bw dose, polymorph nuclear infiltrates, hemosiderin macrophages, and interstitial space thickening were present. In the repeated dose study, all rats survived the 28-day treatment period and apparently showed no signs of toxicity. The hematological and biochemical parameters were not altered. The histopathological study of the organs showed severe changes in the lung, with the dose of 500 mg/kg/day; in the other organs, no alterations were observed or the changes were slight. The body weight was only altered in male rats given the 500 mg/kg dose. The relative weight of the organs did not show any significant changes. Our studies revealed that the essential oil of Thymus vulgaris has moderate oral toxicity according to the results of the acute test, whereas the results of the 28-day oral toxicity test suggest that the no-observed-adverse effect level (NOAEL) is greater than 250 mg/kg/day.

SCHWARZ METHOD FOR SINGULARLY PERTURBED SECOND ORDER CONVECTION-DIFFUSION EQUATIONS

ROJA, J. CHRISTY,TAMILSELVAN, A. The Korean Society for Computational and Applied M 2018 Journal of applied mathematics & informatics Vol.36 No.3

In this paper, we have constructed an overlapping Schwarz method for singularly perturbed second order convection-diffusion equations. The method splits the original domain into two overlapping subdomains. A hybrid difference scheme is proposed in which on the boundary layer region we use the central finite difference scheme on a uniform mesh while on the non-layer region we use the mid-point difference scheme on a uniform mesh. It is shown that the numerical approximations which converge in the maximum norm to the exact solution. When appropriate subdomains are used, the numerical approximations generated from the method are shown to be first order convergent. Furthermore it is shown that, two iterations are sufficient to achieve the expected accuracy. Numerical examples are presented to support the theoretical results. The main advantages of this method used with the proposed scheme is it reduces iteration counts very much and easily identifies in which iteration the Schwarz iterate terminates.