6,288 research outputs found
Higher Order Approximation to the Hill Problem Dynamics about the Libration Points
An analytical solution to the Hill problem Hamiltonian expanded about the
libration points has been obtained by means of perturbation techniques. In
order to compute the higher orders of the perturbation solution that are needed
to capture all the relevant periodic orbits originated from the libration
points within a reasonable accuracy, the normalization is approached in complex
variables. The validity of the solution extends to energy values considerably
far away from that of the libration points and, therefore, can be used in the
computation of Halo orbits as an alternative to the classical
Lindstedt-Poincar\'e approach. Furthermore, the theory correctly predicts the
existence of the two-lane bridge of periodic orbits linking the families of
planar and vertical Lyapunov orbits.Comment: 28 pages, 8 figure
Deep into the Water Fountains: The case of IRAS 18043-2116
(Abridged) The formation of large-scale (hundreds to few thousands of AU)
bipolar structures in the circumstellar envelopes (CSEs) of post-Asymptotic
Giant Branch (post-AGB) stars is poorly understood. The shape of these
structures, traced by emission from fast molecular outflows, suggests that the
dynamics at the innermost regions of these CSEs does not depend only on the
energy of the radiation field of the central star. Deep into the Water
Fountains is an observational project based on the results of programs carried
out with three telescope facilities: The Karl G. Jansky Very Large Array
(JVLA), The Australia Telescope Compact Array (ATCA), and the Very Large
Telescope (SINFONI-VLT). Here we report the results of the observations towards
the WF nebula IRAS 180432116: Detection of radio continuum emission in the
frequency range 1.5GHz - 8.0GHz; HO maser spectral features and radio
continuum emission detected at 22GHz, and H ro-vibrational emission lines
detected at the near infrared. The high-velocity HO maser spectral
features, and the shock-excited H emission detected could be produced in
molecular layers which are swept up as a consequence of the propagation of a
jet-driven wind. Using the derived H column density, we estimated a
molecular mass-loss rate of the order of Myr. On the
other hand, if the radio continuum flux detected is generated as a consequence
of the propagation of a thermal radio jet, the mass-loss rate associated to the
outflowing ionized material is of the order of 10Myr.
The presence of a rotating disk could be a plausible explanation for the
mass-loss rates estimated.Comment: 10 pages, 5 figures. Accepted for publication in A&
Desarrollo y validación de la escala de relajación-mindfulness para adolescentes (EREMIND-A)
Indexación: Scopus.Background: The aim of this investigation was to validate the Relaxation- Mindfulness Scale for Adolescents (EREMIND-A), consisting of 18 items and three factors (Attention-Concentration in the present moment; Relaxation (abilities and attitudes); and Sensory awareness/Contemplation/ Interiority). Method: The validation was done with a sample of Secondary Education and Baccalaureate students from four different centres in Spain (n = 1.120). EFA and CFA of the EREMIND-A were performed and construct and incremental validities calculated. Results: Initial results confi rm the validity and reliability of the scale. Conclusions: There is a need for a broader conceptualization of mindfulness, as well as the inclusion and analysis of other related and cross-cutting concepts. The research in this sense will propitiate the adaptation of the Mindfulness- Based Interventions to the reality of the adolescents in the educational centers, where relaxation and the interiority are aspects to be taken into consideration. © 2018 Psicothema.Antecedentes: el objetivo de esta investigación fue validar la Escala de relajación-Mindfulness para Adolescentes (EREMIND-A), que contiene 18 ítems y tres factores (Atención-Concentración en el momento presente; Relajación (habilidades y actitudes); Consciencia Sensorial/Contemplación/Interioridad. Método: la validación se realizó con una muestra de estudiantes de Educación Secundaria y Bachillerato de cuatro centros diferentes en España (n = 1.120). Se realizaron análisis factoriales exploratorios y confirmatorios de la escala y se calcularon la validez de constructo e incremental. Resultados: los resultados iniciales confirman la fiabilidad y validez de la escala. Conclusiones: es necesaria una conceptualización más amplia de la atención plena, así como la inclusión y análisis de otros conceptos relacionados y transversales. La investigación en este sentido propiciará la adaptación de las intervenciones basadas en mindfulness a la realidad de los adolescentes en los centros educativos, donde la relajación y la interioridad son aspectos a tener en consideración.http://www.psicothema.com/pdf/4475.pd
Optical amplification enhancement in photonic crystals
Improving and controlling the efficiency of a gain medium is one of the most
challenging problems of laser research. By measuring the gain length in an opal
based photonic crystal doped with laser dye, we demonstrate that optical
amplification is more than twenty-fold enhanced along the Gamma-K symmetry
directions of the face centered cubic photonic crystal. These results are
theoretically explained by directional variations of the density of states,
providing a quantitative connection between density of the states and light
amplification
The Kuramoto model: A simple paradigm for synchronization phenomena
Synchronization phenomena in large populations of interacting elements are the subject of intense research efforts in physical, biological, chemical, and social systems. A successful approach to the problem of synchronization consists of modeling each member of the population as a phase oscillator. In this review, synchronization is analyzed in one of the most representative models of coupled phase oscillators, the Kuramoto model. A rigorous mathematical treatment, specific numerical methods, and many variations and extensions of the original model that have appeared in the last few years are presented. Relevant applications of the model in different contexts are also included
Optimal light harvesting structures at optical and infrared frequencies
One-dimensional light harvesting structures with a realistic geometry
nano-patterned on an opaque metallic film are optimized to render high
transmission efficiencies at optical and infrared frequencies. Simple design
rules are developed for the particular case of a slit-groove array with a given
number of grooves that are symmetrically distributed with respect to a central
slit. These rules take advantage of the hybridization of Fabry-Perot modes in
the slit and surface modes of the corrugated metal surface. Same design rules
apply for optical and infrared frequencies. The parameter space of the groove
array is also examined with a conjugate gradient optimization algorithm that
used as a seed the geometries optimized following physical intuition. Both
uniform and nonuniform groove arrays are considered. The largest transmission
enhancement, with respect to a uniform array, is obtained for a chirped groove
profile. Such enhancement is a function of the wavelength. It decreases from
39% in the optical part of the spectrum to 15% at the long wavelength infrared.Comment: 13 pages, 5 figure
Circulating kisspeptin and anti-müllerian hormone levels, and insulin resistance in women with polycystic ovary syndrome: a systematic review, meta-analysis, and meta-regression
Objective: This systematic review and meta-analysis aimed to summarize the available evidence regarding circulating kisspeptin and anti-müllerian hormone (AMH) and the homeostasis model assessment of insulin resistance (HOMA-IR) index in adolescents and women with and without polycystic ovary syndrome (PCOS). Method: We performed a comprehensive literature search in Medline, Embase, Cochrane, Scopus, and Web of Science for studies evaluating circulating kisspeptin levels in women with and without PCOS published until September 24th, 2020. Co-primary outcomes were the HOMA-IR index and AMH. The quality of included studies was assessed using the Newcastle-Ottawa Scale. Random-effects models were used to estimate outcomes, and effects reported as mean difference (MD) or standardized MD (SMD) and their 95 % confidence interval (CI). The systematic review and meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO) as number CRD42020205030. Results: We evaluated 18 studies including, 1282 PCOS cases and 977 controls. Participants with PCOS were younger (MD = −2.38 years, 95 %CI -4.32 to -0.44), with higher BMI (MD = 1.16, 95 % CI 0.54–1.78), waist-to-hip ratio (MD = 0.04, 95 %CI 0.02 to 0.05), circulating kisspeptin (SMD = 1.15, 95 %CI 0.68–1.62), luteinizing hormone (SMD = 1.29, 95 %CI 0.76–1.83), AMH (SMD = 0.97, 95 %CI 0.60–1,34), total testosterone (SMD = 2.48, 95 %CI 1.73–3.23), free testosterone (SMD = 1.37, 95 %CI 0.56–2.17), and dehydroepiandrosterone sulphate (SMD = 0.72, 95 %CI 0.32–1.13) levels, and Ferriman-Gallwey score (SMD = 5.08, 95 %CI 2.76–7.39), and lower sex hormone-binding globulin level (SMD = −1.34, 95 %CI −2.15 to −0.52). Besides, participants with PCOS had higher HOMA-IR index (SMD = 0.76, 95 %CI 0.35–1.17), and circulating insulin (SMD = 0.75, 95 %CI 0.30–1.19), leptin (SMD = 2.82, 95 %CI 1.35–4.29), and triglycerides (SMD = 2.15, 95 %CI 1.08–3.23) levels than participants without the syndrome. The meta-regression did not identify significant factors influencing circulating kisspeptin. Conclusion: Patients with PCOS showed higher kisspeptin, LH, insulin, AMH, and androgen levels and HOMA-IR index, and lower sex hormone-binding globulin levels than those without the syndrome
The effect of endometriosis on sexual function as assessed with the Female Sexual Function Index: systematic review and meta-analysis
Aim: To systematically compare sexual function between non-treated women with and without endometriosis.
Methods: A systematic review was performed on PubMed/Medline, Scopus, EMBASE, Web of Science and Cochrane Library databases searching studies that analyzed sexual function (assessed with the 19-item Female Sexual Function Index [FSFI]), and dyspareunia, chronic pelvic pain and dysmenorrhea (assessed with a visual analogue scale [VAS]) in women with and with endometriosis.
Results: In 4 studies, non-treated women with endometriosis presented a higher risk of female sexual dysfunction (mean total FSFI score = 26.55; OR = 2.38; 95% confidence interval [CI] = 1.12, 5.04). Although mean total FSFI scores were not significantly different between women with and without endometriosis (mean difference [MD] = -2.15; 95% CI -4.96, 0.67); all FSFI domain scores were significantly lower in women with endometriosis (n = 4 studies): desire (MD = -0.43; 95% CI -0.57, -0.19); arousal (MD = -0.66; 95% CI -1.15, -0.17); lubrication (MD = -0.41; 95% CI -0.79, -0.02); orgasm (MD = -0.40; 95% CI -0.73, -0.06); satisfaction (MD = -0.45; 95% CI -0.72, -0.18); and pain (MD = -1.03; 95% CI -1.34, -0.72). Women with endometriosis displayed differences (more severity) in terms of VAS scores (2 studies) for dyspareunia (MD = 1.88; 95% CI 0.38, 3.37) and chronic pelvic pain (MD = 2.92; 95% CI 1.26, 4.58); but not for dysmenorrhea.
Conclusion: Non-treated women with endometriosis displayed altered sexual function as evidenced by lower scores in all FSFI domains, and severity of dyspareunia and chronic pelvic pain
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