436 research outputs found

    Laser Microprinting of Transparent and Weakly Absorbing Solutions

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    A laser-based technique for printing transparent andweakly absorbing liquids is developed. Its principleof operation relies in the tight focusing of shortlaser pulses inside the liquid and close to its freesurface, in such a way that the laser radiation isabsorbed in a tiny volume around the beam waist,with practically no absorption in any other locationalong the beam path. If the absorbed energyovercomes the optical breakdown threshold, acavitation bubble is generated, and its expansionresults in the propulsion of a small fraction of liquidwhich can be collected on a substrate, leading to theprinting of a microdroplet for each laser pulse. Thetechnique does not require the preparation of theliquid in thin film form, and its forward mode ofoperation imposes no restriction concerning theoptical properties of the substrate. We demonstratethat the technique is capable of printingmicrodroplets with good resolution, reproducibilityand control, and analyze the influence of the mainprocess parameters. The mechanisms of liquidprinting are also investigated: time-resolvedimaging provides a clear picture of the dynamics ofliquid transfer which allows understanding the mainfeatures observed in the printed droplets

    Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy

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    Copolymer networks with methacrylate main chain and caprolactone and ethylene glycol side groups were obtained by free radical copolymerisation of caprolactone methacrylate (CLMA) and poly(ethylene glycol) methacrylate (PEGMA). Dielectric relaxation spectroscopy was used to analyse molecular mobility of the different groups in the system. Only one main dielectric relaxation process was found in CLMA/PEGMA copolymer networks, located between those of the corresponding homonetworks, indicating that the system does not present phase separation. The copolymers show a secondary relaxation process at temperatures below −50 °C, which can be assigned to the overlapping of the corresponding secondary processes for the homopolymer networks; one of them was related to the local mobility of caprolactone units in CLMA and the second one was assigned to the twisting motions within ethylene glycol moiety in PEGMA. Besides the relaxation processes, the mobility of space charges has been analysed by means of conductivity and electric modulus formalisms.The support from the Spanish Ministry of Economy and Competitiveness (MINECO) and FEDER funds under the project MAT2012-38359-C03-01 is gratefully acknowledged.Sabater I Serra, R.; Escobar Ivirico, JL.; Romero Colomer, FJ.; Andrio Balado, A.; Gómez Ribelles, JL. (2014). Molecular dynamics in polymer networks containing caprolactone and ethylene glycol moieties studied by dielectric relaxation spectroscopy. Journal of Non-Crystalline Solids. 404:109-115. https://doi.org/10.1016/j.jnoncrysol.2014.08.013S10911540

    Seasonal and interannual variability of dissolved oxygen around the Balearic Islands from hydrographic data

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    Oceanographic data obtained between 2001 and 2011 by the Spanish Institute of Oceanography (IEO, Spain) have been used to characterise the spatial distribution and the temporal variability of the dissolvedoxygen around the Balearic Islands (Mediterranean Sea). The study area includes most of the Western Mediterranean Sea, from the Alboran Sea to Cape Creus,atthe border between France and Spain. Dissolved Oxygen (DO) at thewatersurface is found to be in a state of equilibrium exchange with the atmosphere. In the spring and summer a subsurface oxygen supersaturation is observed due to the biological activity, above the subsurface fluorescence maximum. Minimum observed values of dissolved oxygen are related to theLevantine Intermediate Waters (LIW). An unusual minimum of dissolved oxygen concentrations were also recorded in the Alboran Sea Oxygen Minimum Zone. The Western Mediterranean Deep Waters (WMDW) and the Western Intermediate Waters (WIW) show higher values of dissolved oxygenthanthe Levantine Intermediate Waters due to their more recent formation. Using these dissolved oxygen concentrations it is possible to showthat the Western Intermediate Waters move southwards across the Ibiza Channel and the deep water circulates around the Balearic Islands. It has also been possible to characterise the seasonal evolution of the different watermassesandtheir dissolved oxygen content in a station in the Algerian sub-basin. Keywords: Ocean circulation, dissolved oxygen, water masses, Western Mediterranean Sea, Balearic SeaPost-print

    Primeras experiencias españolas con el uso de los ANTIVEGF intravítreos en la retinopatía del prematuro. Estudio multicéntrico

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    Objetivo: Evaluar el pronóstico anatómico de los niños con retinopatía del prematuro (ROP) tratados con inyecciones intraoculares de antiVEGF y laser. Metodo: Estudio multicéntrico, intervencional y retrospectivo. En el estudio se incluyeron 15 ojos de 12 prematuros con ROP de alto riesgo de 6 hospitales diferentes. De ellos, 17 recibieron fotocoagulación e inyección intraocular de dos formas diferentes: Grupo 1.Tratamiento combinado. Siete ojos. Ambas técnicas se aplicaron en un intervalo menor de 10 días. Grupo 2. Tratamiento postlaser. Siete ojos. Pacientes en los que seguía progresando la retinopatía después de la fotocoagulación (la inyección se efectuó, de media, 37,4 días después). El pronóstico se estableció por la necesidad de vitrectomía y por el resultado anatómica retiniano final. Se efectuó un estudio estadístico comparativo entre ambos grupos con test no paramétricos (U Mann-Withney y Chi2). Resultados: Grupo 1. Se dio laser y se puso la inyección intraocular a los 83,2 y 84,7 días de media, respectivamente. (37,8 y 38,7 semanas postmenstruales-PM-). Grupo 2. Se fotocoaguló a los 70,1 días (36,4 semanas PM) y la inyección intraocular se inyectó a los 107,5 días (41,8 semanas PM). Sólo 4 ojos necesitaron vitrectomía, todos pertenecientes al grupo 1 (57,1 %) y por tanto ninguno del grupo 2 (p=0,07). Evolucionaron a pliegue macular o desprendimiento de retina el 14,3 % del grupo 1 y el 71,4 % del grupo 2 (p=0,1). Conclusiones: La inyección intravítrea de antiVEGF con fotocoagulación fue más efectiva que cuando se administra en casos de ojos no respondedores a la fotocoagulaciónObjective: To assess the anatomical outcome of babies with retinopathy of prematurity (ROP) treated with laser and intravitreal injection of antiVEGF. Methods: Retrospective, interventional, multicenter trial. The study included 15 eyes of twelve preterm infants with high risk ROP (from 6 hospitals). Fourteen eyes received intravitreal injections of antiVEGF (bevacizumab or pegaptanib sodium) and laser photocoagulation in two different regimes: Group 1 - combined treatment - (7 eyes). Laser and antiVEGF injections were performed in less than 10 days. Group 2 - postlaser treatment - (7 eyes). Patients with progressive ROP despite peripheral laser ablation (injection antiVEGF, -mean- 37.4 days after). The results were evaluated for the need of more surgery and the final retinal anatomical status. Outcomes for the 2 treatment groups were compared using parametric tests (U Mann-Whitney and Chi2). Results: Group 1. Retinal photocoagulation and intraocular injection were performed at 83.2 and 84.7 days (mean values) or 37.8 and 38.7 weeks (mean values) (postmenstrual age -PMA-). Group 2. Babies underwent photocoagulation at 70.1 days (mean) [36.4 weeks PMA] and injection at 107.5 days [41.8 w. PMA]. Four eyes of group 2 needed vitrectomy (57.1 %) but none in group1 (p=0,07). Macular fold or retinal detachment developed in 14.3 % of group 1 and 71.4 % of group 2 (p=0,1). Conclusion: Intravitreal injection of antiVEGF with photocoagulation was more effective than intravitreal injection in eyes unresponsive to photocoagulatio

    Resting-state frontostriatal functional connectivity in Parkinson's disease-related apathy

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    Background: One of the most common neuropsychiatric symptoms in PD is apathy, affecting between 23 and 70% of patients and thought to be related to frontostriatal dopamine deficits. In the present study, we assessed functional resting-state frontostriatal connectivity and structural changes associated with the presence of apathy in a large sample of PD subjects and healthy controls, while controlling for the presence of comorbid depression and cognitive decline. Methods: Thirty-one healthy controls (HC) and 62 age, sex and education-matched PD patients underwent resting-state functional MRI. Apathy symptoms were evaluated with the Apathy Scale (AS). The 11 Beck Depression Inventory-II items that measure dysphoric mood symptoms as well as relevant neuropsychological scores were used as nuisance factors in connectivity analyses. Voxel-wise analyses of functional connectivity between frontal lobes (limbic, executive, rostral motor and caudal motor regions), striata (limbic, executive, sensorimotor regions) and thalami were performed. Subcortical volumetry/shape analysis and fronto-subcortical voxel-based morphometry were performed to assess structural changes. Results: Twenty-five PD patients were classified as apathetic (PD-A) (AS>13). PD-A patients showed functional connectivity reductions compared with HC and with non-apathetic patients (PD-NA), mainly in left-sided circuits, and predominantly involving limbic striatal and frontal territories. Similarly, severity of apathy negatively correlated with connectivity in these circuits. No significant effects were found in structural analyses. Conclusions: Our results indicate that the presence of apathy in PD is associated with functional connectivity reductions in frontostriatal circuits, predominating in the left hemisphere and mainly involving its limbic components

    Asymmetric Dark Matter and Dark Radiation

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    Asymmetric Dark Matter (ADM) models invoke a particle-antiparticle asymmetry, similar to the one observed in the Baryon sector, to account for the Dark Matter (DM) abundance. Both asymmetries are usually generated by the same mechanism and generally related, thus predicting DM masses around 5 GeV in order to obtain the correct density. The main challenge for successful models is to ensure efficient annihilation of the thermally produced symmetric component of such a light DM candidate without violating constraints from collider or direct searches. A common way to overcome this involves a light mediator, into which DM can efficiently annihilate and which subsequently decays into Standard Model particles. Here we explore the scenario where the light mediator decays instead into lighter degrees of freedom in the dark sector that act as radiation in the early Universe. While this assumption makes indirect DM searches challenging, it leads to signals of extra radiation at BBN and CMB. Under certain conditions, precise measurements of the number of relativistic species, such as those expected from the Planck satellite, can provide information on the structure of the dark sector. We also discuss the constraints of the interactions between DM and Dark Radiation from their imprint in the matter power spectrum.Comment: 22 pages, 5 figures, to be published in JCAP, minor changes to match version to be publishe

    Evolution of electronic and ionic structure of Mg-clusters with the growth cluster size

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    The optimized structure and electronic properties of neutral and singly charged magnesium clusters have been investigated using ab initio theoretical methods based on density-functional theory and systematic post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. We have systematically calculated the optimized geometries of neutral and singly charged magnesium clusters consisting of up to 21 atoms, electronic shell closures, binding energies per atom, ionization potentials and the gap between the highest occupied and the lowest unoccupied molecular orbitals. We have investigated the transition to the hcp structure and metallic evolution of the magnesium clusters, as well as the stability of linear chains and rings of magnesium atoms. The results obtained are compared with the available experimental data and the results of other theoretical works.Comment: 30 pages, 10 figures, 3 table
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