Size distribution and frustrated antiferromagnetic coupling effects on the magnetic behavior of ultrafine akaganéite (β-FeOOH) nanoparticles

The magnetic properties of low dimensional materials of several iron oxyhydroxide phases, such as akaganéite (β-FeOOH) or lepidocrocite (γ-FeO(OH)), remain poorly explored, probably due to their specific preparation as single crystalline phase requires special conditions owing to their structural instability. In the present work, ultrafine akaganéite nanoparticles were prepared by the hydrolysis of FeCl3 solutions at room temperature induced by the presence of NaOH. The resulting product was characterized by several analytical techniques. Structural investigations using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) revealed that the sample was mainly constituted by rather-equiaxial akaganéite nanocrystals with mean diameter of 3.3 ± 0.5 nm. In addition, a small amount of rodlike akaganéite particles with 23 ± 5 nm in length and 5 ± 1 nm in width was also detected. The study of the respective dependences of the dc magnetization and the ac susceptibility on temperature and exciting magnetic field revealed complex magnetic relaxation processes, high coercivity values at low temperature, and exchange bias effect. These results have been tentatively explained considering size distribution effects and the presence of superparamagnetic and spin glass-like contributions arising from the frustration of the antiferromagnetic order owing to surface effects and an insufficient filling of the akaganéite channels with Cl- anions.Financial support from the Mexican Council of Science and Technology (CONACYT) and Universidad Autonoma de Nuevo León under research projects CB12-179486 and PAICYT-CE793-11, respectively, is acknowledged. Spanish funding under the MINECO research project MAT2010-20798-C05-04 and FEDER is also acknowledged.Peer Reviewe

Evaluación de la aplicación de agua de mar para mejorar el CBR de la subrasante afirmada

The main human settlements in Peru lack paved roads or affirmed carriage trails for the continuous or safe movement of vehicles. In this work, the evaluation of the application of seawater in the affirmed subgrade is exposed. Laboratory tests have been carried out, managing to see that the most important indicator of the resistance of the tracks helps in a significant way to improve the California Bearing Ratio (CBR). The results using with drinking water are 64.30%, 78.30%, and 95.20% of CBR and with seawater much higher CBR values of 99.20%, 90.90%, and 109.10%, for which an improvement of 34.90% was obtained and with this it is concluded that the addition of seawater significantly increases the California Bearing Ratio (CBR) of the affirmed subgrade. Keywords: Seawater, affirmed subgrade, CBR, road infrastructure. References [1]D. Flórez, and B. Bernabé, “El agua de mar en la alimentación y la terapéutica,” Sociedad Española de hidrología médica, vol. 30, no. 1, pp. 37-55, 2014. [2]J. Domenech, “Control de la calidad del agua”, Offarm, vol. 21, no. 10, pp. 138-146, 2002. [3]M. Bernardo et al., “Valoración terapéutica del agua de mar en modelos experimentales como terapia complementaria en anemia”, Medica UIS, vol 27, no. 3, pp. 9-18, 2014. [4]A. Fernández, “El agua: un recurso esencial”, Química Viva, vol 11, no. 3, pp. 147-170, 2012. [5]J. Miranda and D. Negrete, “Estabilización de suelos cohesivos con el uso de cloruro de calcio , Pontifica Universidad Católica del Ecuador, Quito, 2011. [6]D. Pumaricra, “Cloruro de magnesio como aditivo en el tratamiento de las propiedades físico mecánicas de la superficie de rodadura en carreteras no pavimentadas”, Pontifica Universidad Católica del Ecuador, Quito. (2019). [7]Ministerio de Transportes y Comunicaciones, “Manual de Carreteras: Suelos, Geología, Geotecnia y Pavimento – Sección Suelos y Pavimentos”, Lima, 2014. [8]C. Gutiérrez, “Estabilización química de carreteras no pavimentadas en el Perú y ventajas comparativas del cloruro de magnesio (bischofita) frente al cloruro de calcio”, Universidad Ricardo Palma, Lima, Perú, 2010. [9]C. Caruajulca, “Influencia del aditivo cloruro de sodio como estabilizante de la subrasante de la carretera tramo cruce el porongo – aeropuerto – Cajamarca”, Universidad Nacional de Cajamarca, Cajamarca, Perú, 2018. [10]C. Chavarry, R. Figueroa and R. Reynaga, “Estabilización química de capas granulares con cloruro de calcio para vías no pavimentadas”, Polo del conocimiento, vol. 5, no. 6, pp. 40-69, 2020. [11]P. Garnica and A. Pérez, “Estabilización de suelos con cloruro de sodio para su uso en las vías terrestres”, Publicación técnica, México, 2002. [12]H. Llerena, “Mejoramiento de una base superficial con cloruro de magnesio hexahidratado”, Universidad Nacional de San Agustín de Arequipa, Arequipa, Perú, 2015. [13]S. Cuadros, “Mejoramiento de las propiedades físico–mecánicas de la subrasante en una vía afirmada de  departamental de la región Junín mediantela estabilización química con óxido de calcio – 2016”, Universidad Peruana los Andes, Huancayo, Perú, 2017. [14]J. Rivera, and R. Mejía, “Estabilización química de suelos - Materiales convencionales y activados alcalinamente”, Informador Técnico, vol. 84, no. 2, pp. 202-226, 2020. [15]G. Thenoux, and S. Vera, “Evaluación de la efectividad del cloruro de magnesio hexahidratado (bischofita) como estabilizador químico de capas de rodadura granulares”, in Consejos Superior de Investigaciones Científicas, p. 1. , 2002.Resumen: Los principales asentamientos humanos en el Perú, carecen de vías pavimentadas o trochas carrozables afirmadas para el desplazamiento de los vehículos de manera continua o segura. En este trabajo se expone la evaluación de la aplicación del agua de mar en la subrasante afirmada. Se han realizado ensayos de laboratorio, logrando ver que si ayuda de manera significativa a mejorar el California Bearing Ratio (CBR) el indicar más importante de la resistencia de las vias. Los resultados utilizando con agua potable son de 64,30%, 78,30% y 95,20% de CBR y con agua de mar valores de CBR mucho más altos de 99,20%, 90,90% y 109,10%, por lo que se obtuvo una mejoría de 34,90% y con ello se concluye que la adición de agua de mar aumenta significativamente el California Bearing Ratio (CBR) de la subrasante afirmada. Palabras Clave: Agua de mar, subrasante afirmada, CBR, infraestructura vial. Referencias [1]D. Flórez, y B. Bernabé, “El agua de mar en la alimentación y la terapéutica,” Sociedad Española de hidrología médica, vol. 30, no. 1, pp. 37-55, 2014. [2]J. Domenech, “Control de la calidad del agua”, Offarm, vol. 21, no. 10, pp. 138-146, 2002. [3]M. Bernardo et al., “Valoración terapéutica del agua de mar en modelos experimentales como terapia complementaria en anemia”, Medica UIS, vol 27, no. 3, pp. 9-18, 2014. [4]A. Fernández, “El agua: un recurso esencial”, Química Viva, vol 11, no. 3, pp. 147-170, 2012. [5]J. Miranda y D. Negrete, “Estabilización de suelos cohesivos con el uso de cloruro de calcio , Pontifica Universidad Católica del Ecuador, Quito, 2011. [6]D. Pumaricra, “Cloruro de magnesio como aditivo en el tratamiento de las propiedades físico mecánicas de la superficie de rodadura en carreteras no pavimentadas”, Pontifica Universidad Católica del Ecuador, Quito. (2019). [7]Ministerio de Transportes y Comunicaciones, “Manual de Carreteras: Suelos, Geología, Geotecnia y Pavimento – Sección Suelos y Pavimentos”, Lima, 2014. [8]C. Gutiérrez, “Estabilización química de carreteras no pavimentadas en el Perú y ventajas comparativas del cloruro de magnesio (bischofita) frente al cloruro de calcio”, Universidad Ricardo Palma, Lima, Perú, 2010. [9]C. Caruajulca, “Influencia del aditivo cloruro de sodio como estabilizante de la subrasante de la carretera tramo cruce el porongo – aeropuerto – Cajamarca”, Universidad Nacional de Cajamarca, Cajamarca, Perú, 2018. [10]C. Chavarry, R. Figueroa y R. Reynaga, “Estabilización química de capas granulares con cloruro de calcio para vías no pavimentadas”, Polo del conocimiento, vol. 5, no. 6, pp. 40-69, 2020. [11]P. Garnica y A. Pérez, “Estabilización de suelos con cloruro de sodio para su uso en las vías terrestres”, Publicación técnica, México, 2002. [12]H. Llerena, “Mejoramiento de una base superficial con cloruro de magnesio hexahidratado”, Universidad Nacional de San Agustín de Arequipa, Arequipa, Perú, 2015. [13]S. Cuadros, “Mejoramiento de las propiedades físico–mecánicas de la subrasante en una vía afirmada de  departamental de la región Junín mediantela estabilización química con óxido de calcio – 2016”, Universidad Peruana los Andes, Huancayo, Perú, 2017. [14]J. Rivera, y R. Mejía, “Estabilización química de suelos - Materiales convencionales y activados alcalinamente”, Informador Técnico, vol. 84, no. 2, pp. 202-226, 2020. [15]G. Thenoux, y S. Vera, “Evaluación de la efectividad del cloruro de magnesio hexahidratado (bischofita) como estabilizador químico de capas de rodadura granulares”, in Consejos Superior de Investigaciones Científicas, p. 1. , 2002

Academic self-efficacy in first year students college of health sciences

Self-efficacy learning is an important component of learning for college. Academic self-efficacy refers to the degree of confidence that health sciences students could successfully complete on college-task. The purpose of this research lies on the specific characteristics of health sciences students according to their academic self-efficacy by comparing their profiles with students that chose a different discipline. The Academic self-efficacy sample was done to 2089 subjects: 902 women and 1187 men, all of them freshmen students from the different careers at the Autonomous University of Chihuahua who responded to a survey questionnaire, with an average age of 18.23 years (SD = 0.74). This is a quantitative approach with a descriptive survey design type. The results obtained by comparing students of health sciences, with students from other disciplines show that perceived self-efficacy in academic behaviors is very similar each other

Reconfigurable all-diffractive optical filters using phase-only spatial light modulators

We demonstrate a reconfigurable optical filter implemented using a phase-only two-dimensional liquid-crystalon-silicon spatial light modulator. To achieve this we utilize two different approaches leading to two different configurations in the modulator. The first one, based on a spatially patterned diffractive lens, permits us to obtain the desired spectrum along the optical axis and, in the second one, which is based on a generalized spectrometer, the desired spectrum is found outside of the optical axis. . In general, these systems are complex, requiring the use of diffractive, refractive, and, in some cases, expensive high-technology components that maybe difficult to align. The spatial light modulator (SLM) could provide an opportunity to change such a situation, because it allows encoding the suitable spatial patterns to generate the desired spectrum in a compact and inexpensive manner. In this Letter, we demonstrate that a single phase-only two-dimensional (2D) SLM can be used as an optical filter. To increase the flexibility, we implemented two different configurations in the SLM. The first one is based on spatially patterned DLs As a first optical filter, we consider the system based on a spatially patterned DL The optical filter based on a spatially patterned DL consists of a circularly symmetric mask and a DL that face each other. The DL can be approximated by a thin lens with a frequency-dependent focal length of value ZðνÞ ¼ Z o ν=ν o , where Z o is the focal length for the frequency ν o . Up to now, this optical filter has been used with fixed masks. Now, with the SLM, we generate userdefined spectra that can be reconfigured with a refresh rate of 60 Hz or above. Let us consider a complex transmittance mask tðrÞ ¼ jtðrÞj exp½iϕðrÞ, with jtðrÞj as the amplitude and ϕðrÞ as the phase of the function. For convenience, we express tðrÞ as a function of a new variable, defined as s ¼ r 2 =a 2 − 0:5, where r refers to the radial coordinate and a is the maximum extension of the mask function. In such a way we define qðsÞ ¼ tðrÞ. We use a polychromatic plane wave of power spectrum SðνÞ to illuminate the optical filter constituted by the combination of this mask with a DL. Under this condition, the on-axis output irradiance I out ðνÞ at the focal plane of the system, located at a distance Z o from the DL, is given by whereQðuÞ ¼ R ∞ −∞ qðsÞ exp½i2πusds is the Fourier transform (FT) of qðsÞ. If Δν ≪ ν o , the leading ν in Eq. (1) can be approximated by ν o . If this approximation does not hold, the influence of the ν factor can be precompensated in the mask design. Now we discuss the mask design. To find a finite aperture complex mask corresponding, through Eq. (1), to a user-defined spectrum, we use the four-step iterative algorithm described in The experimental setup is basically composed of a laser system, an SLM, and an optical spectrum analyzer

Effective demagnetizing tensors in arrays of magnetic nanopillars

A model describing the effect of magnetic dipolar interactions on the susceptibility of magnetic nanopillars is presented. It is an extension of a recently reported model for three-dimensional randomlike dispersions of nearly spherical nanoparticles in equilibrium [Sánchez et al., Phys. Rev. B 95, 134421 (2017)2469-995010.1103/PhysRevB.95.134421], to well-ordered arrays of nanoparticles out of equilibrium. To test it, a high-quality benchmark consisting of a two-dimensional hexagonal arrangement of quasi-identical parallel nickel nanopillars embedded in a porous alumina template was fabricated. This model is based on an effective demagnetizing tensor, which only depends on a few morphological parameters of the sample, as the nearest-neighbor distance between pillars and the volume fraction of pillars in the specimen. It allows us to obtain the nanopillar intrinsic susceptibility tensor from the magnetic response of the nanopillar ensemble. The values of the in-plane and normal-to-plane susceptibility of the sample are successfully predicted by the model. Furthermore, the model reproduces the susceptibility in the applied field direction, measured for different applied field angles. In this way, it provides a simple and accurate treatment to account for the complex magnetic effects produced by dipolar interactions.Facultad de Ciencias ExactasInstituto de Física La Plat

Del contexto cultural al funcionamiento familiar. Conocimientos compartidos y relaciones familiares en adolescentes con intento de suicidio

El objetivo de este texto es identificar y comparar la estructura semántica del dominio cultural, el conocimiento promedio y el grado de consenso cultural sobre las causas del intento de suicidio, los síntomas previos y las estrategias de prevención del intento de suicidio, además evaluar el funcionamiento familiar entre adolescentes mexicanos con y sin intento de suicidio. Se presenta un estudio mixto metodológicamente que usa la técnica de listas libres y el inventario de recursos familiares en una muestra propositiva de 65 adolescentes (13 a 18 años) divididos en dos grupos: el grupo de adolescentes con tentativa suicida y un grupo control con adolescentes estudiantes sin antecedentes de conductas suicidas. Los problemas familiares fueron la principal causa del intento suicida, mientras que la depresión y la tristeza fueron síntomas previos a una tentativa suicida en ambos grupos. La ayuda psicológica y el desarrollo de habilidades de escucha en los padres fueron señaladas como las estrategias para la prevención del suicidio. Respecto del funcionamiento familiar, los adolescentes con tentativa suicida percibieron más conflictos familiares y menor comunicación y apoyo en sus familias en comparación con el grupo control. Los resultados sugieren un conocimiento compartido culturalmente sobre las causas, los síntomas y las estrategias de prevención del intento de suicidio en los adolescentes, el cual se confirma en la percepción del funcionamiento familiar. La familia, elemento central en la cultura mexicana, debe ser considerada en las estrategias de prevención del intento de suicidio en los adolescentes en México. AIM: The aim of the study was to identify and to compare the semantic structure of the cultural domain, the average knowledge and the degree of cultural consensus regarding knowledge of suicide attempts cause, symptoms and prevention strategies to suicide attempt and the family functioning among Mexican adolescents with and without previous suicide attempt. Method: It was a mixed study, using the free-listing technique and an inventory of family resources, with a non-random sample of 65 adolescents (13-18 years) divided in two groups. The suicide attempters group and the control group were high school students, without a history of suicide behaviors. Results: Family problems were identified as the most important cause of suicide attempts in both groups, while depression and sadness were identified as symptoms prior to the suicide attempt in both groups. Psychological aid and development of listening skills in the parents were the most frequent responses regarding prevention strategies to suicide attempt. Regarding family functioning teenage suicide attempters showed more family conflict, less family communication and support than teenage non suicide attempters. Conclusions: The results suggest a same cultural knowledge background regarding causes, symptoms prior and prevention strategies to suicide attempt in Mexican adolescents. Mexican culture centered in family relationships is important to be considered in design of prevention strategies to suicide attempt in adolescence in Mexico.ITESO, A.C

Antibiotic Susceptibility of Biofilm Cells and Molecular Characterisation of Staphylococcus hominis Isolates from Blood

Objectives We aimed to characterise the staphylococcal cassette chromosome mec (SCCmec) type, genetic relatedness, biofilm formation and composition, icaADBC genes detection, icaD expression, and antibiotic susceptibility of planktonic and biofilm cells of Staphylococcus hominis isolates from blood. Methods The study included 67 S. hominis blood isolates. Methicillin resistance was evaluated with the cefoxitin disk test. mecA gene and SCCmec were detected by multiplex PCR. Genetic relatedness was determined by pulsed-field gel electrophoresis. Biofilm formation and composition were evaluated by staining with crystal violet and by detachment assay, respectively; and the biofilm index (BI) was determined. Detection and expression of icaADB Cgenes were performed by multiplex PCR and real-time PCR, respectively. Antibiotic susceptibilities of planktonic cells (minimum inhibitory concentration, MIC) and biofilm cells (minimum biofilm eradication concentration, MBEC) were determined by the broth dilution method. Results Eighty-five percent (57/67) of isolates were methicillin resistant and mecA positive. Of the mecA-positive isolates, 66.7% (38/57) carried a new putative SCCmec type. Four clones were detected, with two to five isolates each. Among all isolates, 91% (61/67) were categorised as strong biofilm producers. Biofilm biomass composition was heterogeneous (polysaccharides, proteins and DNA). All isolates presented the icaD gene, and 6.66% (1/15) isolates expressed icaD. This isolate presented the five genes of ica operon. Higher BI and MBEC values than the MIC values were observed for amikacin, vancomycin, linezolid, oxacillin, ciprofloxacin, and chloramphenicol. Conclusions S. hominis isolates were highly resistant to methicillin and other antimicrobials. Most of the detected SCCmec types were different than those described for S. aureus. Isolates indicated low clonality. The results indicate that S. hominis is a strong biofilm producer with an extracellular matrix with similar composition of proteins, DNA and N-acetylglucosamine; and presents high frequency and low expression of icaD gene. Biofilm production is associated with increased antibiotic resistance

Amyloid-b peptide on sialyl-LewisX-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface

Increased deposition of amyloid-b peptide (Ab) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer’s disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewisx (sLex) were employed to investigate Ab-altered mechanics of membrane tethers formed by bonding between sLex and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Ab to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Ab to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Ab lowered the overall force of membrane tether formation (Fmtf), and produced a bimodal population of Fmtf, suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Ab and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf. In addition, these cerebral endothelial alterations induced by Ab were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Ab to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB.This work was supported by Alzheimer Association Grant NIRG-06-24448; NIH Grant 1P01 AG18357, R21NS052385, 5R21AG032579 and in part by 1P01HL095486 and AHA 0835676N; ‘‘Bolashak’’ scholarship and Ministry of Education and Science of the Republic of Kazakhstan 1029/GF2. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Novelty, challenge, and practice:The impact of intensive language learning on attentional functions

We investigated the impact of a short intensive language course on attentional functions. We examined 33 participants of a one-week Scottish Gaelic course and compared them to 34 controls: 16 active controls who participated in courses of comparable duration and intensity but not involving foreign language learning and 18 passive controls who followed their usual routines. Participants completed auditory tests of attentional inhibition and switching. There was no difference between the groups in any measures at the beginning of the course. At the end of the course, a significant improvement in attention switching was observed in the language group (p < .001) but not the control group (p = .127), independent of the age of participants (18-78 years). Half of the language participants (n = 17) were retested nine months after their course. All those who practiced Gaelic 5 hours or more per week improved from their baseline performance. In contrast, those who practiced 4 hours or fewer showed an inconsistent pattern: some improved while others stayed the same or deteriorated. Our results suggest that even a short period of intensive language learning can modulate attentional functions and that all age groups can benefit from this effect. Moreover, these short-term effects can be maintained through continuous practice