Search

Gain measurements are carried out for different lengths of three types of erbium-doped silica fiber with different pump powers at 1480 nm. From these measurements a relation is established for each type of fiber between gain and the attenuation factor of the pump power. This relation is in complete agreement with the one predicted by an analytic model based on overlapping factors, which makes it possible to obtain methods for the experimental characterization of doped fibers.

A simple model describing the evolution of pump, signal, and amplified spontaneous emission powers in an erbium-doped silica fiber is presented. The model is based on overlapping factors, depending on pump- and signal-coupled powers, which are systematically studied. Accurate results for gain and amplified spontaneous emission are obtained when this model is used. Experiment to measure the characteristic parameters of the fiber appearing in the model ar described. Two main advantages of this model are found: computation time is considerably reduced and fiber characterization does not make it necessary to measure the parameters of the fiber as a function of radial or azimuthal coordinates.

The purpose of this paper was to assess the reliability of four standard stereotests and evaluate them by means of their failure rates. Near stereoacuity in 200 healthy young volunteers (24±8 years), was measured with Titmus, Randot, TNO, and Frisby tests. The stereoacuity provided by these four tests were evaluated. Stereoacuity by the normal population, with a limit of 85% of the people, rises 70" with Randot and 120" with TNO independently of gender. Females achieve 80" with Titmus and 30" with Frisby and males reach 140" and 40" with Titmus and Frisby respectively. Failure rates lower than 10% were obtained by all the tests. This study finds differences among stereoacuity measured with different tests and recommends performing, at least, two types of test to evaluate each person. [ABSTRACT FROM AUTHOR]

A new theoretical model based on the standard-model equations but ensuring conservation of energy by accounting for the optical powers stored in the laser cavity is presented. This model succeeds in grouping two sorts of previous models: those based on standard equations and those based on conservation of number of photons. Furthermore, it provides a more complete quantitative description of EDSFLs (erbium-doped silica fibre lasers) and also improves the qualitative description of these devices by including the spontaneous emission terms and by determining the optical powers involved as well as the oscillation wavelength. The possibility of solving the EDSFL system including the power modal distribution within the fibre is also considered. Finally, a detailed comparison between this model and the models proposed by other authors is shown, where it is proved that the new model describes much better the behaviour of EDSFLs. [ABSTRACT FROM AUTHOR]

In this article several characterization techniques developed by the authors for erbium-doped fibers and integrated waveguides are discussed. These techniques are used to obtain the input parameters in the theoretical models that have been developed, too. In this way optical amplifiers and lasers are studied and optimized for different applications. Comparisons between computed values and experimental results are presented. [ABSTRACT FROM AUTHOR]

We report a study on the main features of a 1.48-mum pumped erbium-doped fiber laser, such as threshold pump power, output power, and slope efficiency. In particular we have focused on its dependence on active fiber length. We employed an all-fiber laser configuration, which included mirrors directly coated onto the polished fiber endfaces. Launched pump power and laser output power were introduced and extracted, respectively, from the laser cavity by means of couplers. Our measure ments show the existence of an optimum erbium-doped fiber length, where threshold power reaches minimum and output power maximum. [ABSTRACT FROM AUTHOR]

Microbiota dysbiosis and metabolic syndrome, consequences of a non-adequate diet, generate a feedback pathogenic state implicated in Alzheimer's disease development. The lower production of short chain fatty acids (SCFAs) under dysbiosis status leads to lipid homeostasis deregulation and decreases Angptl4 release and AMPK activation in the adipose tissue, promoting higher lipid storage (adipocyte hypertrophy) and cholesterol levels. Also, low SCFA generation reduces GPR41 and GPR43 receptor activation at the adipose tissue (increasing leptin release and leptin receptor resistance) and intestinal levels, reducing the release of GLP-1 and YPP. Therefore, lower satiety sensation and energy expenditure occur, promoting a weight gaining environment mediated by higher food intake and lipid storage, developing dyslipemia. In this context, higher glucose levels, together with higher free fatty acids in the bloodstream, promote glycolipotoxicity, provoking a reduction in insulin released, insulin receptor resistance, advanced glycation products (AGEs) and type 2 diabetes. Intestinal dysbiosis and low SCFAs reduce bacterial biodiversity, increasing lipopolysaccharide (LPS)-producing bacteria and intestinal barrier permeability. Higher amounts of LPS pass to the bloodstream (endotoxemia), causing a low-grade chronic inflammatory state characterized by higher levels of leptin, IL-1β, IL-6 and TNF-α, together with a reduced release of adiponectin and IL-10. At the brain and neuronal levels, the generated insulin resistance, low-grade chronic inflammation, leptin resistance, AGE production and LPS increase directly impact the secretase enzymes and tau hyperphosphorylation, creating an enabling environment for β-amyloid senile plaque and tau tangled formations and, as a consequence, Alzheimer's initiation, development and maintenance.

Objective: To determine whether patients with drug-resistant mesial temporal lobe epilepsy present with an alteration in the autonomic circadian regulation of blood pressure., Methods: A prospective case‒control study was designed, with a case group comprising patients with drug-resistant mesial temporal lobe epilepsy and a control group comprising healthy volunteers. Twenty-four-hour outpatient blood pressure monitoring was performed to assess the existence of a normal (dipping) or altered (non-dipping) circadian pattern. In addition, analytical and ultrasound parameters (carotid intima-media thickness) of vascular risk and sleep quality were evaluated., Results: Twenty-four subjects were recruited in each study group, amongst whom no demographic differences or history of vascular risk were observed. A higher percentage of participants with a non-dipping pattern was observed in the group of patients with epilepsy (62.5% vs. 12.5, p = 0.001). In the case group, significant differences were also observed in carotid intima-media thickness, with a greater probability of presenting with pathological values (p = 0.022)., Conclusion: The results suggest a disorder of the central autonomic control of blood pressure in patients with drug-resistant mesial temporal lobe epilepsy, with a greater probability of developing an alteration of the circadian rhythm of blood pressure. This dysfunction may be a factor involved in the increased cardiovascular risk in this population., Competing Interests: Declaration of Competing Interest All authors declare that they have no conflicts of interest., (Copyright © 2023. Published by Elsevier Ltd.)

An optical fiber-based supercontinuum setup and a custom-made spectrophotometer that can measure spectra from 1100 to 2300 nm, are used to describe attenuation properties from different ex vivo rat tissues. Our method is able to differentiate between scattering and absorption coefficients in biological tissues. Theoretical assumptions combined with experimental measurements demonstrate that, in this infrared range, tissue attenuation and absorption can be accurately measured, and scattering can be described as the difference between both magnitudes. Attenuation, absorption, and scattering spectral coefficients of heart, brain, spleen, retina, and kidney are given by applying these theoretical and experimental methods. Light through these tissues is affected by high scattering, resulting in multiple absorption events, and longer wavelengths should be used to obtain lower attenuation values. It can be observed that the absorption coefficient has a similar behavior in the samples under study, with two main zones of absorption due to the water absorption bands at 1450 and 1950 nm, and with different absolute absorption values depending on the constituents of each tissue. The scattering coefficient can be determined, showing slight differences between retina and brain samples, and among heart, spleen and kidney tissues.

Near-infrared supercontinuum generation by using silica-based highly-nonlinear fiber placed inside of the ring-cavity of an erbium-doped fiber laser pulsed by mode-locking is experimentally demonstrated. Only one erbium-doped fiber amplifier is employed to generate supercontinuum with a spectral width as long as 830 nm (from 1205 to 2035 nm) and a spectral power higher than -30  dBm/nm. To generate supercontinuum, it is not necessary a second amplifier to raise the power of the laser pulses coupled into the nonlinear fiber. Moreover, all the devices employed are commercial and available at any photonics laboratory. To the best of our knowledge, this is the first demonstration of this kind of device by pumping the nonlinear fiber in the third window of communications.

Osteomyelitis is a rare infection that is considered to be a children’s disease. Diagnosis is frequently delayed because it is an uncommon pathology and is presented in various ways. After its diagnosis and treatment, the result is favourable in children. We present a clinical case that shows difficulties in its diagnosis. A high index of suspicion should be addressed for early recognition.

We have characterised 997 hip fracture patients from a representative 45 Spanish hospitals, and followed them up prospectively for up to 4 months. Despite suboptimal surgical delays (average 59.1 hours), in-hospital mortality was lower than in Northern European cohorts. The secondary fracture prevention gap is unacceptably high at 85%., Purpose: To characterise inpatient care, complications, and 4-month mortality following a hip or proximal femur fracture in Spain., Methods: Design: prospective cohort study. Consecutive sample of patients ≥ 50 years old admitted in a representative 45 hospitals for a hip or proximal femur fragility fracture, from June 2014 to June 2016 and followed up for 4 months post-fracture. Patient characteristics, site of fracture, in-patient care (including secondary fracture prevention) and complications, and 4-month mortality are described., Results: A total of 997 subjects (765 women) of mean (standard deviation) age 83.6 (8.4) years were included. Previous history of fracture/s (36.9%) and falls (43%) were common, and 10-year FRAX-estimated major and hip fracture risks were 15.2% (9.0%) and 8.5% (7.6%) respectively. Inter-trochanteric (44.6%) and displaced intra-capsular (28.0%) were the most common fracture sites, and fixation with short intramedullary nail (38.6%) with spinal anaesthesia (75.5%) the most common procedures. Surgery and rehabilitation were initiated within a mean 59.1 (56.7) and 61.9 (55.1) hours respectively, and average length of stay was 11.5 (9.3) days. Antithrombotic and antibiotic prophylaxis were given to 99.8% and 98.2% respectively, whilst only 12.4% received secondary fracture prevention at discharge. Common complications included delirium (36.1 %) and kidney failure (14.1%), with in-hospital and 4-month mortality of 2.1% and 11% respectively., Conclusions: Despite suboptimal surgical delay, post-hip fracture mortality is low in Spanish hospitals. The secondary fracture prevention gap is unacceptably high at > 85%, in spite of virtually universal anti-thrombotic and antibiotic prophylaxis.

Purpose: Metaphyseal titanium sleeves have been used to provide cementless fixation in challenging bone defects in revision knee arthroplasty. The aim of this study was to evaluate the mid-term results of radiological and clinical outcomes, for metaphyseal sleeves in type 1B and 2 defects of tibia and femur under the hypothesis that they would provide stable and prolonged fixation., Methods: One hundred and thirty-four patients were included in a prospective study to evaluate the outcomes of knee revision with sleeves, together with stems and varus-valgus constrained mobile bearing prosthesis. Median follow-up was 71.5 months (range 36-107). Analysis included American Knee Society Score (KSS), Western Ontario and Mcmaster Universities Osteoarthritis Index (WOMAC), SF12 Health Survey and radiographic assessment., Results: All clinical scores improved significantly in all patients during the follow-up. The median of Knee KSS increased from 33 to 78 and functional KSS from 30 to 80. The median of WOMAC pain index changed from 12 to 4; pre-operative median of WOMAC stiffness and WOMAC function score improved from 5 to 2 and from 45 to 14, respectively. The median of physical SF12 varied from 27 to 44, while mental SF-12 from 43 to 54. Radiological evaluation showed optimal osseous integration in all patients, and neither implant migration nor progressive radiolucency around components was observed. Complications included three cases of end-of-stem pain at tibial side and two revisions due to septic loosening in the first post-operative year. No aseptic loosening was reported., Conclusion: The use of metaphyseal sleeves, in combination with uncemented stems and varus-valgus constrained components with rotating platform, has shown excellent mid-term results allowing osseous ingrowth with no evidence of osteolysis or displacement. This is a promising option for better implant fixation in revision TKA., Level of Evidence: Case series with no comparison group, Level IV.