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1.
MethodsX ; 13: 102918, 2024 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-39253001

RESUMEN

The present article provides an improvement in the method to correct indirect strain measurements in triaxial compressive strength tests through axial displacement and hydraulic fluid volume change measurements. The improvement focused on reducing the parameters of the formula proposed for indirect volumetric strain in the original method, thereby facilitating the development of a simpler formula in which the radial strain depends on only two parameters: the initial volume of the rock specimen and the volume changes of the hydraulic fluid for each instant. The comparison between the improvement proposed, and original method resulted in a mean absolute difference of 0.003.•This improvement does not depend on the axial strain, unlike the original method, which requires correcting the indirect axial strain measurements before correcting the indirect radial strain measurements.•This improvement can be useful for research on the stress-strain behavior of intact rock under laboratory conditions, such as in the study of the post-peak state.

2.
J Nutr Health Aging ; 27(10): 806-807, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37960902
3.
J Frailty Aging ; 12(4): 291-297, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38008979

RESUMEN

AIM: To verify the inter-rater agreement of the Integrated Care for Older People (ICOPE) STEP 1 screening tool using the ICOPE Monitor app, comparing self-assessment to a screening performed by a health professional. METHODS: We compared the results of the ICOPE Step 1 obtained by self-screening with those obtained by a professional screening using Gwet's agreement coefficient in two studies. Study 1 tested inter-rater reliability in participants to the INSPIRE-T cohort who agreed to undergo the self-and the professional screening on the same day. Study 2 used data from the INSPIRE-ICOPE care cohort. We included real-life users of the French health system whose first ICOPE Step 1 was a self-assessment followed by a professional Step 1within 130 days (mean=76 days, SD=60). RESULTS: Study 1 included 79 participants (45 aged less than 60, 34 aged 60 and over, 60% female, mean (SD) age of 54.5 (18.5) years). Of the 207 participants in Study 2, 49 were less than 60, and 158 were 60 and over (54% female, mean (SD) age 67 (16.1) years). Agreement coefficients in Study 1 ranged from 0.49 (CI95% 0.24; 0.66) in the cognition domain - moderate agreement) to 0.99 (CI95% 0.96;1.00) in the nutrition domain - very good agreement); and in Study 2 from 0.36 (CI95% 0.23;0.49) in the cognition domain to 0.97 (95% 0.95;1.00) in the nutrition domain. The agreement coefficients for the cognition and hearing domains were higher for the participants aged <60 than those aged 60 and over. The time orientation items (cognition) showed high reliability. CONCLUSION: Our study supports using ICOPE Step 1 as a self-assessment screening tool. High reliability was found for intrinsic capacity's nutrition, psychological, and locomotion domains, regardless of age. We discuss aspects of the self-assessment of cognition, vision, and hearing domains when using the ICOPE monitor app in older adults.


Asunto(s)
Aplicaciones Móviles , Humanos , Femenino , Persona de Mediana Edad , Anciano , Masculino , Reproducibilidad de los Resultados , Estado Nutricional
4.
Int. j. morphol ; 41(3): 838-844, jun. 2023. ilus, tab
Artículo en Español | LILACS | ID: biblio-1514296

RESUMEN

Las restricciones por la pandemia del COVID-19 supusieron la transición abrupta a una enseñanza online tanto del contenido teórico como práctico y de la evaluación final de las asignaturas que imparte el departamento en varias titulaciones. En previsión de que el siguiente curso académico 2020-21 se vería totalmente afectado, se desarrollaron una serie de materiales didácticos propios, como la elaboración de guiones de teoría y práctica que incorporaron imágenes de modelos anatómicos, prosecciones, anatomía radiológica y anatomía ecográfica. La percepción de esta innovación fue evaluada por los estudiantes a través de una encuesta en línea y sus respuestas mediante una escala tipo Likert. Participaron 346 estudiantes de las titulaciones de Fisioterapia (n= 66), Medicina (n= 169), Podología (n= 44) y Terapia Ocupacional (n= 67). Las puntuaciones medias más altas correspondieron a los estudiantes de Podología y Terapia Ocupacional, ambas presentaron diferencias significativas con los otros tres subgrupos de alumnos (p<.0001). El puntaje promedio más bajo correspondió a los estudiantes de Medicina de segundo año académico que presentó significancia con los otros cuatro subgrupos de estudiantes (p<.0001). Se analizaron las carencias del sistema educativo en la Universidad Complutense de Madrid reveladas por la pandemia del Covid19. Esta crisis ha puesto de manifiesto la necesidad de que los educadores médicos en general y los anatomistas en particular estén capacitados en el uso de la tecnología disponible y en la creación de sus propios materiales didácticos multimedia.


SUMMARY: Restrictions due to COVID-19 pandemic meant an abrupt transition to online teaching. This change affected teaching, practical sessions and assessments of the subjects taught by the department in various degrees. In anticipation that the following academic year 2020-21 would be totally affected, a series of didactic materials were therefor developed. These materials included the preparation of theory and practice scripts that incorporated images of anatomical models, pro-sections, radiological anatomy, and ultrasound anatomy. Perceptions by the students of these innovations were recorded through an online survey and their responses evaluated through a Likert-type scale. 346 students from Physiotherapy (n= 66), Medicine (n= 169), Podiatry (n= 44) and Occupational Therapy (n= 67) degrees participated. The highest average scores corresponded to the students of Podiatry and Occupational Therapy, both presented significant differences with the other three subgroups of students (p<.0001). The lowest average score corresponded to medical students in their second academic year, which presented significance with the other four subgroups of students (p<.0001). The shortcomings of the educational system of the Complutense University of Madrid that were highlighted by the COVID-19 pandemic were analyzed. This crisis underscored the need for medical educators in general, and anatomists in particular, to be trained in the use of available technology and to produce their own multimedia teaching materials.


Asunto(s)
Humanos , Estudiantes/psicología , Educación a Distancia/métodos , COVID-19 , Anatomía/educación , Percepción , España , Estudios Transversales , Encuestas y Cuestionarios , Evaluación Educacional
6.
J Frailty Aging ; 12(1): 1-6, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36629077

RESUMEN

The Appetite loss in older people is an important unmet clinical need in geriatrics. The International Conference on Frailty and Sarcopenia Research (ICFSR) organized a Task Force on April 20th 2022, in Boston, to discuss issues related to appetite loss in older people, in particular, the assessment tools currently available, its evaluation in the primary care setting, and considerations about its management. There is a high heterogeneity in terms of the etiology of appetite loss in older people and a gold standard assessment tool for evaluating this condition is still absent. Although this may render difficult the management of poor appetite in clinical practice, validated assessment tools are currently available to facilitate early identification of appetite loss and support care decisions. As research on biomarkers of appetite loss progresses, assessment tools will soon be used jointly with biomarkers for more accurate diagnosis and prognosis. In addition, efforts to foster the development of drugs with a favorable risk/benefit ratio to combat poor appetite should be strengthened.


Asunto(s)
Fragilidad , Sarcopenia , Humanos , Anciano , Sarcopenia/diagnóstico , Sarcopenia/complicaciones , Fragilidad/complicaciones , Apetito , Anorexia , Biomarcadores
7.
J Nutr Health Aging ; 27(10): 806-807, 2023 09 23.
Artículo en Inglés | MEDLINE | ID: mdl-38216222
8.
J Frailty Aging ; 10(2): 94-102, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33575697

RESUMEN

BACKGROUND: The screening tool of the Integrated Care for Older People (ICOPE Step 1), designed to detect declines in the domains of intrinsic capacity, has been incipiently investigated in older adult populations. OBJECTIVES: To retrospectively estimate the frequency of priority conditions associated with declines in intrinsic capacity according to an adaptation of the screening tool ICOPE Step 1 among participants of the Multidomain Alzheimer Preventive Trial (MAPT). DESIGN: A cross-sectional retrospective analysis from the baseline assessment of the MAPT. SETTING: The data was gathered during a preventive consultation for cardiovascular risk factors in memory clinics in France. PARTICIPANTS: Seven hundred fifty-nine older adults aged 70-89 years with memory complaints, allocated to the multidomain groups of the MAPT study. MEASUREMENTS: Five domains of intrinsic capacity (cognition, locomotion, nutrition, sensorial, and psychological) were assessed using a screening tool similar to the ICOPE Step 1 (MAPT Step 1). The frequency of six conditions associated with declines in intrinsic capacity (cognitive decline, limited mobility, malnutrition, visual impairment, hearing loss, and depressive symptoms) was obtained for older adults with memory complaints participating in the MAPT study. RESULTS: Overall, 89.3% of the participants had one or more conditions associated with declines in intrinsic capacity. The overall frequency of each condition was: 52.2% for cognitive decline, 20.2% for limited mobility, 6.6% for malnutrition, 18.1% for visual impairment, 56.2% for hearing loss, and 39% for depressive symptoms. CONCLUSION: After being screened with an adaptation of the ICOPE step 1 (MAPT step 1) tool, 9/10 older adults had one or more conditions associated with declines in intrinsic capacity. The relative frequency differs across conditions and could probably be lower in a population without memory complaints. The frequency of screened conditions associated with declines in IC highlights how relevant it is to develop function-centered care modalities to promote healthy aging.


Asunto(s)
Disfunción Cognitiva , Prestación Integrada de Atención de Salud , Evaluación Geriátrica , Tamizaje Masivo , Anciano , Anciano de 80 o más Años , Disfunción Cognitiva/diagnóstico , Disfunción Cognitiva/epidemiología , Estudios Transversales , Francia/epidemiología , Humanos , Tamizaje Masivo/métodos , Estudios Retrospectivos , Factores de Riesgo
9.
J Nutr Health Aging ; 25(1): 33-40, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33367460

RESUMEN

OBJECTIVES: The aim of this study was to compare a short and a long version of an intrinsic capacity index and test their cross-sectional association with relevant health outcomes in older adults. DESIGN: Cross-sectional analysis of the baseline data of the FraDySMex study. PARTICIPANTS: 543 community-dwelling adults aged 50 years and older living in 2 municipalities in Mexico City, from which 435 had complete data on the variables of interest. METHODS: The intrinsic capacity indices were obtained using principal components analysis. The performance of the indices was tested respective to frailty, IADL and ADL. RESULTS: The short and long versions of the IC index performed well for assessing functional status. Using biometrical variables like the phase angle, grip strength and gait speed measured by the GAIT rite improved the index performance vis a vis IADL disability (Lawton), but not to the other evaluated outcomes. CONCLUSIONS: Both the long and short versions of the intrinsic capacity indices tested were able to classify older adults according to their functional status and were associated with relevant health outcomes.


Asunto(s)
Fragilidad/epidemiología , Vida Independiente/normas , Anciano , Estudios Transversales , Femenino , Humanos , Masculino , México , Reproducibilidad de los Resultados , Estudios Retrospectivos , Resultado del Tratamiento
10.
J Nutr Health Aging ; 24(9): 959-965, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33155621

RESUMEN

OBJECTIVES: Intrinsic capacity is a composite of five domains that summarizes the physical and mental capacities of an individual. Intrinsic capacity is increasing in relevance for adapting health systems to population ageing. Therefore, our objective was to analyse how intrinsic capacity has been assessed in older adults and if these measurements have been validated, as an initial step towards the construction of a standard intrinsic capacity index. DESIGN: Narrative review with electronic searches performed in PubMed and Cochrane databases, including the studies which used the term "intrinsic capacity" in the context of human ageing and health. The full text was then accessed to select studies with at least one operationalised domain of intrinsic capacity. We also looked for information on the validity and reliability of the reported measures of intrinsic capacity. RESULTS: We included ten articles reporting a quantitative measurement of intrinsic capacity. There were two intrinsic capacity scores which combined retrospective data on the intrinsic capacity domains sub-scores, with low concordance among tests chosen to measure each domain. Two studies reported on reliability and validity of the IC scores. The main gaps in the construction and validation process were a) analysis undertaken with each domain separately rather than for the construct of intrinsic capacity, b) lack of a clear conceptual and operational definition of the vitality domain, c) summary score that depends upon the distribution of the study sample. CONCLUSION: Further validation of the intrinsic capacity concept is needed, together with more robust approaches to measure it. A standard index of IC has not been validated for translation into clinical or research purposes.


Asunto(s)
Salud Pública/métodos , Estándares de Referencia , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Estudios Retrospectivos
11.
J Phys Condens Matter ; 31(43): 435702, 2019 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-31242475

RESUMEN

We construct the Barut-Girardello coherent states for charge carriers in anisotropic 2D-Dirac materials immersed in a constant homogeneous magnetic field which is orthogonal to the sample surface. For that purpose, we solve the anisotropic Dirac equation and identify the appropriate arising and lowering operators. Working in a Landau-like gauge, we explicitly construct nonlinear coherent states as eigenstates of a generalized annihilation operator with complex eigenvalues which depends on an arbitrary function f  of the number operator. In order to describe the anisotropy effects on these states, we obtain the Heisenberg uncertainty relation, the probability density, mean energy value and occupation number distribution for three different functions f . For the case in which the anisotropy is caused by uniaxial strain, we obtain that when the stress is applied along the x-axis of the material surface, the probability density for the nonlinear coherent states is smaller compared to when the material is stressed along the orthogonal axis.

12.
Constr Build Mater ; 151: 186-195, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-28860680

RESUMEN

During steam curing of concrete, temperature and moisture gradients are developed, which are difficult to measure experimentally and can adversely affect the durability of concrete. In this research, a model of cement hydration coupled to moisture and heat transport was used to simulate the process of steam curing of mortars with water-to-cement (w/c) ratios by mass of 0.30 and 0.45, considering natural convection boundary conditions in mortar and concrete specimens of AASHTO Type VI beams. The primary variables of the model were moisture content, temperature, and degree of hydration. Moisture content profiles of mortar specimens (40 mm in diameter and 50 mm in height) were measured by magnetic resonance imaging. The degree of hydration was obtained by mass-based measurements of loss on ignition to 1000 °C. The results indicate that the model correctly simulates the moisture distribution and degree of hydration in mortar specimens. Application of the model to the steam curing of an AASHTO Type VI beam indicates temperature differences (between the surface and the center) higher than 20 °C during the cooling stage, and internal temperatures higher than 70 °C that may compromise the durability of the concrete.

13.
Cem Concr Compos ; 69: 38-48, 2016 May.
Artículo en Inglés | MEDLINE | ID: mdl-27022208

RESUMEN

A model that describes hydration and heat-mass transport in Portland cement mortar during steam curing was developed. The hydration reactions are described by a maturity function that uses the equivalent age concept, coupled to a heat and mass balance. The thermal conductivity and specific heat of mortar with water-to-cement mass ratio of 0.30 was measured during hydration, using the Transient Plane Source method. The parameters for the maturity equation and the activation energy were obtained by isothermal calorimetry at 23 °C and 38 °C. Steam curing and semi-adiabatic experiments were carried out to obtain the temperature evolution and moisture profiles were assessed by magnetic resonance imaging. Three specimen geometries were simulated and the results were compared with experimental data. Comparisons of temperature had maximum residuals of 2.5 °C and 5 °C for semi-adiabatic and steam curing conditions, respectively. The model correctly predicts the evaporable water distribution obtained by magnetic resonance imaging.

14.
Opt Lett ; 40(10): 2397-400, 2015 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-26393749

RESUMEN

We report a compact, stable, high-power, picosecond ultraviolet (UV) source at 266 nm based on simple single-pass two-step fourth-harmonic generation (FHG) of a mode-locked Yb-fiber laser at 79.5 MHz in LiB3O5 (LBO) and ß-BaB2O4. Using a 30-mm-long LBO crystal for single-pass second-harmonic generation, we achieve up to 9.1 W of average green power at 532 nm for 16.8 W of Yb-fiber power at a conversion efficiency of 54% in 16.2 ps pulses with a TEM00 spatial profile and passive power stability better than 0.5% rms over 16 h. The generated green radiation is then used for single-pass FHG into the UV, providing as much as 1.8 W of average power at 266 nm under the optimum focusing condition in the presence of spatial walk-off, at an overall FHG conversion efficiency of ∼11%. The generated UV output exhibits passive power stability better than 4.6% rms over 1.5 h and beam pointing stability better than 84 µrad over 1 h. The UV output beam has a circularity of >80% in high beam quality with the TEM00 mode profile. To the best of our knowledge, this is the first report of picosecond UV generation at 266 nm at megahertz repetition rates.


Asunto(s)
Láseres de Estado Sólido , Rayos Ultravioleta , Fenómenos Ópticos , Factores de Tiempo
15.
Dev Comp Immunol ; 53(2): 271-82, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26188097

RESUMEN

Polymeric immunoglobulins (pIgs) mucosal secretion is mediated by the pIg secretory immune system (PISIS), which is composed of J-chain (JC) and antibody (IgM/IgA) producing cells (JC-AbPC), pIg receptor (pIgR) epithelial cell expression and the efficient release of secretory Igs (SIgs) to the mucosal lumen. A poor development or disturbances in this system may cause higher infection susceptibility, as observed in young and elderly people. In spite of this system's importance, few detailed studies regarding its development have been described in the lower respiratory tract of humans. Because the porcine model has been reported as an option for translational medicine to humans, we studied the tracheal and bronchial PISIS development in healthy, non-vaccinated, SPF, miniature Vietnamese pigs from birth to adulthood using immunohistochemistry and ELISAs. Our results demonstrated that pIgR was present at birth, and its expression increased with age. In contrast, JC-AbPC were low in neonatal pigs; however, colostrum was a source of IgM, SIgA, total IgA and IgG in respiratory secretions (trachea and bronchoalveolar lavages, nasal secretion and saliva) in piglets. JC-AbPC steadily increased in post-weaned, young and adult pigs, correlating with considerable increases in secretory and total Igs in the trachea and bronchi. These data suggest a compensatory role of maternal Igs at the respiratory mucosa in the absence of a structured PISIS before weaning. Furthermore, monomeric Igs (IgG and IgA) may also play an important role in respiratory protection and deserves a more thorough study.


Asunto(s)
Bronquios/inmunología , Sistema Inmunológico/metabolismo , Receptores de Inmunoglobulina Polimérica/metabolismo , Mucosa Respiratoria/metabolismo , Tráquea/inmunología , Animales , Animales Recién Nacidos , Formación de Anticuerpos , Calostro/metabolismo , Humanos , Sistema Inmunológico/crecimiento & desarrollo , Inmunidad Materno-Adquirida , Inmunoglobulina A Secretora/metabolismo , Inmunoglobulina G/metabolismo , Inmunoglobulina M/metabolismo , Modelos Animales , Porcinos , Porcinos Enanos
16.
Opt Lett ; 40(3): 403-6, 2015 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-25680058

RESUMEN

We report a stable, high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 355 nm based on single-pass sum-frequency generation of a mode-locked Yb-fiber laser at 1064 nm in the nonlinear crystal BiB3O6. By performing single-pass second-harmonic generation (SHG) in a 30-mm-long LiB3O5 crystal, up to 9.1 W of average green power at 532 nm is obtained at a single-pass SHG efficiency of 54%. The generated green pulses have a duration of 16.2 ps at a repetition rate of 79.5 MHz, with a passive power stability better than 0.5% rms and a pointing stability <12 µrad over 1 h, in high beam quality. The green radiation is then sum-frequency-mixed with the fundamental in a 10-mm-long BiB3O6 crystal, providing as much as 1.2 W of average UV power, at an infrared-to-UV conversion efficiency of 7.2%, with a passive power stability better than 0.4% rms over 3 h and a pointing stability <45 µrad over 1 h, in TEM00 spatial profile.


Asunto(s)
Bismuto , Compuestos de Boro , Láseres de Estado Sólido , Fibras Ópticas , Óxidos , Iterbio , Amplificadores Electrónicos
17.
J Nutr Health Aging ; 17(4): 390-2, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23538664

RESUMEN

OBJECTIVES: This study on flavor enhancers aims to: 1) compare food intake of older persons, 2) determine changes in body weight, blood pressure and serum sodium and 3) determine tolerance/intolerance to the flavor enhancers. DESIGN: The project is a cross-over, double blind study design. SETTING: A nursing home for the aged, Golden Acres Institution located in Quezon City, Philippines. PARTICIPANTS: Sixty eligible subjects (31 males and 29 females), aged 60 years and over. INTERVENTION: Subjects were initially given: pouch A (0.5gram monosodium glutamate) or pouch B (0.5gram iodized salt) for lunch and supper for 2 months. The intervention was switched after one week wash period. MEASUREMENTS: Before the start and during intervention, 24 hour food intake of subjects was recorded and anthropometric and clinical data were measured. Tolerance/intolerance to the flavor enhancer and data on the quality of life were evaluated using a pre-tested structured questionnaire. Paired t-test was used to determine significant changes among each period of dietary intervention between different groups. RESULTS: Energy intake and almost all nutrients increased for males and females for both interventions. Body weight and body mass index increased significantly for both gender with MSG usage but not with iodized salt. The diastolic blood pressure of all subjects was normal while the systolic blood pressure remained at pre-hypertension level before and after both interventions. The sodium serum was within normal levels for both groups for both interventions. It was also observed that systolic blood pressure increased in both groups while sodium levels did not. It was further observed that both MSG and iodized salt interventions were well tolerated by majority of the participants. CONCLUSION: The use of flavor enhancers have increased food intake and were well- tolerated among older persons. No difference in blood pressure and sodium serum was noted in both MSG and iodized salt intake. RECOMMENDATION: People with less appetite, especially among older persons can use flavor enhancers to improve their food intake and body weight. Sodium containing flavor enhancers can be part of a healthy diet for older persons when used in moderation.


Asunto(s)
Aromatizantes/administración & dosificación , Hogares para Ancianos , Casas de Salud , Estado Nutricional , Anciano , Antropometría , Apetito , Presión Sanguínea/efectos de los fármacos , Estudios Cruzados , Método Doble Ciego , Ingestión de Energía , Femenino , Humanos , Yodo/administración & dosificación , Masculino , Filipinas , Prehipertensión , Sodio/sangre , Cloruro de Sodio Dietético/administración & dosificación , Glutamato de Sodio/administración & dosificación , Encuestas y Cuestionarios , Gusto
18.
Eur J Clin Nutr ; 66(8): 914-9, 2012 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-22692025

RESUMEN

BACKGROUND/OBJECTIVES: Infant feeding decisions made by new parents have significant health implications. The study aimed to investigate: influences on infant feeding decisions; characteristics of mothers reporting reliance on alternative information sources; associations between reliance on different sources and intentions to exclusively breastfeed and introduce complementary foods later; and subsequent breastfeeding and weaning behaviours. SUBJECTS/METHODS: First-time mothers in five European countries (England, Finland, Germany, Hungary, Spain) completed questionnaires about the importance of 17 influences on infant feeding choices at birth and 8 months later, during 2007-2008. Use of individual sources and reliance on four categories (family and friends, health professionals, written materials, audio-visual media) were compared between countries. Associations between information sources used and mother characteristics, feeding intentions and behaviours were investigated using appropriate statistical tests. RESULTS: In all, 2071 first-time mothers provided baseline data; 78% at 8 months. Variation exists between countries in the influence of different sources on feeding decisions of first-time mothers. Across all countries, the most important influences at both time points were books, partner and antenatal midwife. Mothers in higher income quintiles and remaining at school beyond age 16 years reported greater reliance on written sources (P<0.0005). Mothers relying most on written sources reported longer exclusive breastfeeding (P=0.002), and a tendency to introduce foods other than milk later (P=0.079) than mothers relying most on personal or professional contacts. CONCLUSION: Further research is required about which dissemination strategies are most effective at improving infant feeding behaviours in varied cultural settings, and for different socio-economic groups.


Asunto(s)
Lactancia Materna/estadística & datos numéricos , Conducta de Elección , Conocimientos, Actitudes y Práctica en Salud , Madres/psicología , Adulto , Lactancia Materna/métodos , Inglaterra , Femenino , Finlandia , Estudios de Seguimiento , Alemania , Humanos , Hungría , Lactante , Estudios Longitudinales , Factores Socioeconómicos , España , Encuestas y Cuestionarios , Destete , Adulto Joven
20.
Opt Lett ; 36(5): 639-41, 2011 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-21368933

RESUMEN

We show that light pulses propagating in two-photon absorbing systems may present time delays like slow light produced via coherent population oscillations in one-photon interactions. Two regimes are numerically studied for a simplified two-level system: (a) a light pulse at frequency ω/2 undergoes two-photon absorption (TPA) and is delayed by the absorbing system (two-photon slow light) and (b) a light pulse at frequency ω is delayed in a system prepared by TPA of a light pulse at frequency ω/2 (two-photon-assisted slow light). The study carried out in solutions of dyes and dendrites shows significant delays, low distortion, and good transmission for easily reachable experimental conditions. The working principle can be applied to other media and can be used in telecommunications technology.

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