White matter integrity related to functional working memory networks in traumatic brain injury

Objective: This study explores the functional and structural patterns of connectivity underlying working memory impairment after severe traumatic axonal injury. Methods: We performed an fMRI n-back task and acquired diffusion tensor images (DTI) in a group of 19 chronic-stage patients with severe traumatic brain injury (TBI) and evidence of traumatic axonal injury and 19 matched healthy controls. We performed image analyses with FSL software and fMRI data were analyzed using probabilistic independent component analysis. Fractional anisotropy (FA) maps from DTI images were analyzed with FMRIB's Diffusion Toolbox. Results: We identified working memory and default mode networks. Global FA values correlated with both networks and FA whole-brain analysis revealed correlations in several tracts associated with the functional activation. Furthermore, working memory performance in the patient group correlated with the functional activation patterns and with the FA values of the associative fasciculi. Conclusion: Combining structural and functional neuroimaging data, we were able to describe structural white matter changes related to functional network alterations and to lower performance in working memory in chronic TBI.MAPFRE FoundationPreprintMedicin

White matter integrity related to functional working memory networks in traumatic brain injury

Objective: This study explores the functional and structural patterns of connectivity underlying working memory impairment after severe traumatic axonal injury. Methods: We performed an fMRI n-back task and acquired diffusion tensor images (DTI) in a group of 19 chronic-stage patients with severe traumatic brain injury (TBI) and evidence of traumatic axonal injury and 19 matched healthy controls. We performed image analyses with FSL software and fMRI data were analyzed using probabilistic independent component analysis. Fractional anisotropy (FA) maps from DTI images were analyzed with FMRIB's Diffusion Toolbox. Results: We identified working memory and default mode networks. Global FA values correlated with both networks and FA whole-brain analysis revealed correlations in several tracts associated with the functional activation. Furthermore, working memory performance in the patient group correlated with the functional activation patterns and with the FA values of the associative fasciculi. Conclusion: Combining structural and functional neuroimaging data, we were able to describe structural white matter changes related to functional network alterations and to lower performance in working memory in chronic TBI

White Matter/Gray Matter Contrast Changes in Chronic and Diffuse Traumatic brain Injury

Signal-intensity contrast of T1-weighted magnetic resonance imaging scans has been associated with tissue integrity and reported as a sign of neurodegenerative changes in diseases such as Alzheimer's disease. After severe traumatic brain injury (TBI), progressive structural changes occur in white (WM) and gray matter (GM). In the current study, we assessed the signal-intensity contrast of GM and WM in patients with diffuse TBI in the chronic stage to (1) characterize the regional pattern of WM/GM changes in intensity contrast associated with traumatic axonal injury, (2) evaluate possible associations between this measure and diffusion tensor image (DTI)/fractional anisotropy (FA) for detecting WM damage, and (3) investigate the correlates of both measures with cognitive outcomes. Structural T1 scans were processed with FreeSurfer software to identify the boundary and calculate the WM/GM contrast maps. DTIs were processed with the FMRIB software library to obtain FA maps. The WM/GM contrast in TBI patients showed a pattern of reduction in almost all of the brain, except the visual and motor primary regions. Global FA values obtained from DTI correlated with the intensity contrast of all associative cerebral regions. WM/GM contrast correlated with memory functions, whereas FA global values correlated with tests measuring memory and mental processing speed. In conclusion, tissue-contrast intensity is a very sensitive measure for detecting structural brain damage in chronic, severe and diffuse TBI, but is less sensitive than FA for reflecting neuropsychological sequelae, such as impaired mental processing speed

Influencia del ángulo limite en la predicción del índice de reducción sonora

[ES] Este trabajo se inscribe en el contexto del esfuerzo por acotar incertidumbres en las predicciones del aislamiento acústico. El objeto del mismo es cuantificar la incertidumbre asociada a la elección del ángulo límite al realizar predicciones del Índice de reducción sonora de una partición. En él se realiza una valoración de la incertidumbre, tanto en función de la frecuencia, como del parámetro ponderado global en decibelios A. El estudio se concreta para el caso de materiales de uso común en la edificación y para el caso de una placa delgada, infinita y elástica, de forma que separa dos regiones del espacio sin que haya conexión alguna entre ambas. La importancia de este término queda reflejada en la cuantificación que se realiza de la incertidumbre para ciertos materiales y ángulos para los cuales puede ser del orden de 3 dB(A).[EN] This work is done in the context of trying to limit the uncertainties in the predictions of the acoustic isolation. Our aim is to quantify the uncertainty due to the choice of the limit angle on the prediction of the Transmission Loss of a partition. We have evaluated how this uncertainty depends on the frequency and on the weighted global parameter in dB(A). Specifically, we have studied in this work material of common use in building and the case of a thin, infinite, and elastic plate that separates two regions of the space without connection between them. The importance of the choice of the limit angle is reflected in the quantification of the uncertainty for certain materials and angles, for which it can be of the order of 3 dB(A).Este trabajo ha sido financiado por el MINISTERIO DE EDUCACION Y CIENCIA -D.G. INVESTIGACION (BIA2007-68098-C02-01 y BIA2007-68098-C02-02)Alba Fernández, J.; Rey Tormos, RMD.; Ramis Soriano, J.; Escuder Silla, EM. (2008). Influencia del ángulo limite en la predicción del índice de reducción sonora. Revista de Acústica. 39(3-4):21-27. http://hdl.handle.net/10251/36173S2127393-

Nuevos materiales absorbentes acústicos basados en fibra de kenaf

Acoustic Standards in the building are responsible for, companies and individuals, propose new acoustic materials for the sound isolation. This paper presents a new sound-absorbent material, it is based on natural fibres, particularly fibres of kenaf. It also proposes an empirical model for this material, this models depends on the frequency. There are accepted models from the scientific community about mineral wool, glass wool, rock wool, foam or polyester fibre. Several of these models are empirical. They are obtained from the equation adjustments about the acoustic impedance and propagation constant behaviour, depending upon the flow resistivity, fibre's diameter and density. There are even standards like UNE-EN 12354-6 where these models are accepted under certain limitations like the fundamental basis as in the materials' acoustics behaviour prediction. From the various tests conducted in the laboratory, empirical equations are proposed for this new acoustic material. In addition, there has been a first approach to validate this model in combination with a micro-structural model, based on the steps taken by Bies-Hansen (1), which allows us to obtain the value of the resistance to flow.This project has been funded by the Ministry of Education and Science. DG Research (BIA2007-C02-01 y BIA2007-C02-02).Ramis Soriano, J.; Alba Fernández, J.; Rey Tormos, RMD.; Escuder Silla, EM.; Sanchis Rico, VJ. (2010). Nuevos materiales absorbentes acústicos basados en fibra de kenaf. Materiales de Construcción. 60(299):133-143. doi:10.3989/mc.2010.50809S13314360299Alcaide, B., & Almendros, P. (2001). 4-Oxoazetidine-2-carbaldehydes as useful building blocks in stereocontrolled synthesis. Chemical Society Reviews, 30(4), 226-240. doi:10.1039/b007908

The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Characterization of impervious layers using scale models and an inverse method

We describe a novel procedure that uses an inverse method to determine unknown parameters for impervious layers used in multilayer structures. The proposed model of the multilayer structure is limited to an ideal double plate separated by an unbonded, fibrous, sound-absorbing material. Experimental data were obtained by nearfield acoustic holography for the calculation of the transmission loss of various multilayer structures mounted in a window in a wooden box designed specifically for this purpose. We used the Trochidis and Kalaroutis forecast model of acoustic insulation for multilayer structures, which is based on a spatial Fourier transform. The experimental pressure and velocity data were used as input data in the inverse method. By applying the Trochidis and Kalaroutis model and using numerical methods to adjust the variables that define the impervious layers of the system, the values of the unknown parameters of the layers could then be calculated. For validation, the results were compared with results obtained using the Ookura and Saito model, based on impedance coupling between layers and using the statistical-energy-analysis model, which subdivides the system into subsystems. We evaluate the measurement errors associated with the construction of a hologram by nearfield acoustic holography, i.e., errors due to sensor mismatch and position mismatch, in terms of their probabilities. © 2009 Elsevier Ltd. All rights reserved.This work was supported by the Ministry of Education and Science (BIA2007-68098-C02-01 and BIA2007-68098-C0202), by Conselleria de Empresa, Universidad y Ciencia (APOSTD/2007/112) and by Conselleria de Educacion de la Generalitat Valenciana (GVPRE/2008/115).Alba Fernández, J.; Escuder Silla, EM.; Ramis Soriano, J.; Rey Tormos, RMD. (2009). Characterization of impervious layers using scale models and an inverse method. Journal of Sound and Vibration. 326(1):190-204. https://doi.org/10.1016/j.jsv.2009.04.045S190204326

Application of the Finite Elements Method for the Simulation of Flanking Transmissions in Joints with Floating Floors

[EN] This paper presents the use of the finite elements method to study the flanking transmission through the use of the vibration reduction index, for the case of constructive solutions that use floating floors. On one side, the insertion of elastic interlayer in new building solutions is now a very common practice. On the other side, the test procedures for the acoustic study of this kind of sets (concrete floor with elastic interlayer) are very laborious and the existing empirical equations do not match reality in many cases. For this reason, the study of the problem using finite elements would allows giving numerical solution to a wide range of different constructive solutions and numerical prediction for the acoustical isolation could be improved.[ES] En este trabajo se plantea el uso del método de los elementos finitos para el estudio de las transmisiones laterales a través del índice de reducción de vibraciones, para el caso de soluciones constructivas con suelos flotantes. Por una parte, la inserción de láminas elásticas en nuevas soluciones constructivas es en la actualidad una práctica muy común. Por otra parte, los procedimientos de ensayo para el estudio acústico de este conjunto (forjado con lámina elástica) son muy laboriosos y las ecuaciones empíricas existentes no satisfacen la realidad en muchos de los casos. Es por este motivo que se plantea el estudio mediante los elementos finitos, lo que nos permitirá dar solución numérica a un gran conjunto de diferentes soluciones constructivas y poder así mejorar las predicciones numéricas para el aislamiento acústico.Este trabajo ha sido financiado por el Ministerio de Educación y Ciencia de España (BIA2007-68098-C02-01 y BIA2007-68098-C02-02).http://dx.doi.org/10.4067/S0718-07642010000600009Rey Tormos, RMD.; Alba Fernández, J.; Ramis Soriano, J.; Escuder Silla, EM. (2010). Aplicación del Método de los Elementos Finitos para la Simulación de las Transmisiones por Flanco en Uniones con Suelos Flotantes. Información Tecnológica. 21(6):67-78. https://doi.org/10.4067/S0718-07642010000600009S677821

Diffusion tensor imaging differences relate to memory deficits in diffuse traumatic brain injury

BACKGROUND: Memory is one of the most impaired functions after traumatic brain injury (TBI). We used diffusion tensor imaging (DTI) to determine the structural basis of memory deficit. We correlated fractional anisotropy (FA) of the fasciculi connecting the main cerebral regions that are involved in declarative and working memory functions. METHODS: Fifteen patients with severe and diffuse TBI and sixteen healthy controls matched by age and years of education were scanned. The neuropsychological assessment included: Letter-number sequencing test (LNS), 2-back task, digit span (forwards and backwards) and the Rivermead profilet. DTI was analyzed by a tract-based spatial statics (TBSS) approach. RESULTS: Whole brain DTI analysis showed a global decrease in FA values that correlated with the 2-back d-prime index, but not with the Rivermead profile. ROI analysis revealed positive correlations between working memory performance assessed by 2-back d-prime and superior longitudinal fasciculi, corpus callosum, arcuate fasciculi and fornix. Declarative memory assessed by the Rivermead profile scores correlated with the fornix and the corpus callosum. CONCLUSIONS: Diffuse TBI is associated with a general decrease of white matter integrity. Nevertheless deficits in specific memory domains are related to different patterns of white matter damage