Correlation-based multiplexing of spectral channels and fiber-optic sensors using unmodulated continuous-wave distributed feedback diode lasers.

In this Letter, we demonstrate a method for the multiplexing of spectral channels and fiber-optic sensors. The method makes use of the correlation-based demultiplexing technique. In our approach, each light source has an inherent phase noise which we propose to use as a "fingerprint" for correlation-based recognition and demultiplexing of spectral channels as well as signals from different sensors in each spectral channel. The proposed method requires for its implementation an extremely simple and robust scheme and can be attractive for budget-sensitive applications. As active elements, it uses only two standard free-running CW distributed feedback (DFB) diode lasers. No modulators or optical filters are required for operation. Results of proof-of-concept experiments are presented for the interrogation of several ultra-weak fiber Bragg gratings (FBGs) with reflectivity of 0.05% in a 4-km-long fiber for temperature measurements with the resolution of 0.1°C.

Passive quadrature demodulation of multiplexed interferometric sensors using a CW correlation reflectometer with a single DFB diode laser.

In this Letter, we report a novel, to the best of our knowledge, and simple approach for passive quadrature-phase demodulation of relatively long multiplexed interferometers based on two-channel coherence correlation reflectometry. Two-wavelength channels are generated using a single unmodulated CW-DFB diode laser and an acousto-optic frequency shifter. The introduced frequency shift determines the optical lengths of the interferometers. In our experiments, all interferometers have the same optical length of 32 cm corresponding to the π/2 phase difference between channel signals. An additional fiber delay line was introduced between channels to destroy coherence between initial and frequency-shifted channels. Demultiplexing of channels and sensors was performed using correlation-based signal processing. Amplitudes of cross correlation peaks obtained for both channels were used to extract the interferometric phase for each interferometer. Phase demodulation of relatively long multiplexed interferometers is experimentally demonstrated. Experimental results prove that the proposed technique is suitable for interrogating a serial array of relatively long interferometers dynamically modulated with phase excursions exceeding 2π. Simultaneous interrogation and phase demodulation were experimentally demonstrated using an in-line array of low-finesse Fabry-Perot interferometric sensors.

Presentación de GeriatriApp: una app para la evaluación geriátrica integral en español / Introducing GeriatriApp: App in Spanish for a comprehensive geriatric assessment

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Constraint percolation on hyperbolic lattices.

Hyperbolic lattices interpolate between finite-dimensional lattices and Bethe lattices, and they are interesting in their own right, with ordinary percolation exhibiting not one but two phase transitions. We study four constraint percolation models-k-core percolation (for k=1,2,3) and force-balance percolation-on several tessellations of the hyperbolic plane. By comparing these four different models, our numerical data suggest that all of the k-core models, even for k=3, exhibit behavior similar to ordinary percolation, while the force-balance percolation transition is discontinuous. We also provide proof, for some hyperbolic lattices, of the existence of a critical probability that is less than unity for the force-balance model, so that we can place our interpretation of the numerical data for this model on a more rigorous footing. Finally, we discuss improved numerical methods for determining the two critical probabilities on the hyperbolic lattice for the k-core percolation models.

Geriatric education in undergraduate and graduate levels in Latin America.

A recent dramatic increase in the elderly population has not been accompanied by a parallel increase in specialized health care professionals in Latin America. The main purpose of this work was to determine the stage of geriatrics teaching for undergraduate and graduate medical levels in Latin America. Using a questionnaire given in person and online, the authors surveyed geriatricians from 16 countries: eight from South America and eight from Central America. Among 308 medical schools, 35% taught undergraduate geriatrics, ranging from none in Uruguay, Venezuela, and Guatemala to 82% in Mexico. The authors identified 36 programs in 12 countries with graduate medical education in geriatrics, ranging from 2 to 5 years of training. The authors conclude that although the population is aging rapidly in Latin American countries, there has been a slow development of geriatrics teaching at undergraduate and postgraduate levels in the region.

Energy barriers and cell migration in densely packed tissues.

Recent observations demonstrate that confluent tissues exhibit features of glassy dynamics, such as caging behavior and dynamical heterogeneities, although it has remained unclear how single-cell properties control this behavior. Here we develop numerical and theoretical models to calculate energy barriers to cell rearrangements, which help govern cell migration in cell monolayers. In contrast to work on sheared foams, we find that energy barrier heights are exponentially distributed and depend systematically on the cell's number of neighbors. Based on these results, we predict glassy two-time correlation functions for cell motion, with a timescale that increases rapidly as cell activity decreases. These correlation functions are used to construct simple random walks that reproduce the caging behavior observed for cell trajectories in experiments. This work provides a theoretical framework for predicting collective motion of cells in wound-healing, embryogenesis and cancer tumorogenesis.

Jamming graphs: a local approach to global mechanical rigidity.

We revisit the concept of minimal rigidity as applied to frictionless, repulsive soft sphere packings in two dimensions with the introduction of the jamming graph. Minimal rigidity is a purely combinatorial property encoded via Laman's theorem in two dimensions. It constrains the global, average coordination number of the graph, for example. However, minimal rigidity does not address the geometry of local mechanical stability. The jamming graph contains both properties of global mechanical stability at the onset of jamming and local mechanical stability. We demonstrate how jamming graphs can be constructed using local moves via the Henneberg construction such that these graphs fall under the jurisdiction of correlated percolation. We then probe how jamming graphs destabilize, or become unjammed, by deleting a bond and computing the resulting rigid cluster distribution. We also study how the system restabilizes with the addition of new contacts and how a jamming graph with extra (redundant) contacts destabilizes. The latter endeavor allows us to probe a disk packing in the rigid phase and uncover a potentially new diverging length scale associated with the random deletion of contacts as compared to the study of cut-out (or frozen-in) subsystems.

El paciente geriátrico y el acto anestésico: nova et vetera / The geriatric patient and the anesthetic act: nova et vetera

A medida que la población envejece, más pacientes geriátricos deben someterse a cirugías, bien sea electivas o urgentes. Dado que el envejecimiento es una experiencia única y personal, cada paciente que va ser sometido a cirugía debe abordarse de manera individual. La valoración de la reserva funcional ha llegado a ser la piedra angular en el plan anestésico y es marcador pronóstico integral. Se dan pautas para su valoración, así como de la capacidad funcional, con el fin de minimizar los riesgos de la anestesia y la cirugía. En la presente revisión se discuten los cambios de los órganos con la edad, el papel de las enfermedades intercurrentes como factores determinantes del riesgo, otros factores que incrementan el riesgo de complicaciones y los problemas perioperatorios que se pueden presentar, entre otros, los relacionados con el estado cognitivo.

As the population ages, more geriatric patients should undergo Esther elective or urgent surgery. Given that ageing is a unique and individual experience, each patient that goes to surgery, must be addressed on an individual basis. The assessment of the functional reserve has become the cornerstone in the anesthetic plan and is the fore-casting integral marker. Guidelines for its assessment are given, as well as its functional capacity, in order to minimize the risks of anesthesia and surgery. In this review, changes in organs with age, the role of intercurrent diseases, and other factors that increase the risk of complications, perioperative problems that may arise, including those related to cognitive stes are discussed.

Morbilidad y mortalidad geriátricas en el Hospital San Juan de Dios de Bogotá

Con el fin de analizar las principales características de la población mayor de 65 años vista en el Hospital San Juan de Dios de Bogotá, se realizó un estudio retrospectivo sobre 632 historias clínicas. El promedio de edad fue de 73.1 años. Apreciamos una relación directa entre la edad y la estancia hospitalaria con un promedio global de 15.9 días-paciente. El diagnóstico de egreso más frecuente fue la enfermedad cerebrovascular (8.2 por ciento), y reuniendo en un solo grupo las enfermedades del sistema cardiovascular, representarían 14 por ciento de los casos. Los traumatismos aparecen como causa importante de morbilidad. La mortalidad global fue de 8.9 por ciento, siendo la enfermedad cerebrovascular y la falla cardíaca con 12 casos cada una, las dos primeras causas de muerte; como dato alarmante la septicemia ocupó el tercer lugar. Se concluye que es necesario fomentar el estudio y la investigación en este grupo poblacional, cada vez más creciente.