Hydrogen production by chemical-looping reforming in a circulating fluidized bed reactor using Ni-based oxygen carriers

7 pages, 11 figures,.- Available online November 18, 2008.This work presents the experimental results obtained during auto-thermal chemical-looping reforming (CLR) in a 900 Wth circulating fluidized bed reactor under continuous operation using methane as fuel. Two oxygen carriers based on NiO and supported on γ-Al2O3 and α-Al2O3 were used during more than 50 h of operation with each oxygen carrier. During operation the effect of different operating variables, like fuel reactor temperature, H2O/CH4 molar ratio and solid circulation rate, on CH4 conversion and gas product distribution was analyzed. It was found that in all operating conditions CH4 conversion was very high (>98%) and the most important variable affecting to the gas product distribution was the solid circulation rate, that is, NiO/CH4 molar ratio. Similar gas product distribution was obtained working with both oxygen carriers although at different NiO/CH4 molar ratios. The oxygen carrier of NiO on α-Al2O3 needed lower NiO/CH4 molar ratio to reach the same gas product composition than the oxygen carrier of NiO on γ-Al2O3. Working at optimal operating conditions, 2.5 moles of H2 per mol of CH4 could be obtained in this process. During operation the oxygen carrier particles maintained their physical and chemical properties. These results suggest that these oxygen carriers could have a high durability, being suitable oxygen carriers for a CLR system. © 2008 Elsevier B.V. All rights reserved.This work was partially supported by the European Commission, under the 6th Framework Programme (CACHET Project, Contract no. 019972), and from the CCP2 (CO2 Capture Project), a partnership of BP, Chevron, Conoco-Phillips, Eni Technology, Norsk Hydro, Shell, Suncor, and Petrobras. M. Ortiz thanks Diputación General de Aragon for the F.P.I. fellowship.Peer Reviewe

Development of a measurement system to detect spine postures under dynamic conditions

Mit der Methode der Rasterstereographie wurde in den 80er Jahren durch Drerup und Hierholzer ein Verfahren entwickelt das mittels einer Oberflächenanalyse des Rückens radiologische und klinische Untersuchungen an der Wirbelsäule bei orthopädischen und orthopädietechnischen Fragestellungen ergänzen kann. Basierend auf dem Prinzip der Triangulation ermöglicht es eine schnelle, berührungslose und großflächige Analyse von Haltungsparametern des Rumpfes. Hierfür werden Veränderungen in Lichtlinien, die durch einen Diaprojektor auf den Rücken des Patienten projiziert werden mit einer Halbleitervideokamera erfasst und dreidimensional rekonstruiert. Durch eine Computersoftware können hieraus Haltungsparameter berechnet werden. Mit dem bisher verwendeten Messgerät können nur Aufnahmen unter statischen Bedingungen durchgeführt werden. Ziel dieser Studie war es daher bestehende Hard- und Softwarekomponenten so weiter zu entwickeln, dass dynamische Bewegungsabläufe erfasst werden können. Zur Evaluierung der Messgenauigkeit des neuen Messsystems, unter dynamischen Bedingungen, wurden auf einer Holzplatte angebrachte Marker vermessen. Bewegt wurde die Holzplatte dabei durch einen computergesteuerten Roboterarm. Insgesamt wurde so die Position der Marker während sieben unterschiedlichen Bewegungsmustern bestimmt. Dabei konnte die sog. "Rumpflänge" bei insgesamt 1090 Einzelmessungen, mit einer Genauigkeit von 3,29 mm bestimmt werden, während der sog. "Lumbalgrübchenabstand" sogar mit einer Genauigkeit von 1,04 mm gemessen werden konnte. Die Überprüfung der Reliabilität des Messgerätes erfolgte durch Wiederholungsmessungen an aktiven Sportlerinnen während ruhigem Stehen und während der Durchführung einer Armkreisbewegung. Dabei ergaben sich Standardabweichungen für die Rumpflänge von 1,92-7,52 mm und für die Rumpfneigung von 0,24-1,02°. Weitere bestimmte Parameter wie der Kyphosewinkel konnten mit einer SD von 0,82-1,79° und der Lordosewinkel mit 1,04-2,99° gemessen werden. Abschließend wurde versucht den modifizierten Haltungstest nach Matthiass durch das neue Messgerät zu objektivieren. Hierfür wurden 31 aktive, haltungsgesunde Tennisspieler untersucht. Um größere Veränderungen in den Haltungsparamtern der Probanden während des Haltungstests zu erzeugen, wurde dieser mit zusätzlichen Gewichten abhängig vom Körpergewicht durchgeführt. Besonders betrachtet wurden dabei Veränderungen der Haltungsparameter zu Beginn und nach Beendigung des Haltungstests. Durch diese Untersuchungen konnte gezeigt werden, dass die Rumpflänge im Durchschnitt bei allen Probanden und Gewichtsstufen während des Haltetests leicht zunimmt. Ebenfalls wurde eine Aufrichtung des Rumpfes beobachtet, verbunden mit einer geringen Abflachung der Brustkyphose und einer leichten Zunahme der Lendenlordose. Mit Hilfe von Korrelationstests konnte nachgewiesen werden, dass Gewichte von 5% des Körpergewichts ausreichend sind, um signifikante Veränderungen in den Haltungsparamtern bei haltungsgesunden Probanden hervorzurufen. Allerdings müssen diese Ergebnisse noch durch Untersuchungen an Haltungsschwachen überprüft werden. Mit dem 4D-Imager scheint ein Messgerät entwickelt worden zu sein, dass präzise, strahlenfreie, kontaktlose und dynamische Untersuchungen von Haltungsparametern ermöglicht. Es bestehen aber noch leichte Ungenauigkeiten bei der automatischen Erkennung des siebten Halswirbels, der als anatomischer Fixpunkt dient, so dass hier noch Verbesserungen ausstehen. Einschränkend ist bisher noch die max. Bildfrequenz von 15 Hz, was den Einsatz des Messgerätes auf langsame bis mittelschnelle Bewegungen limitiert. Zu beachten ist außerdem die noch relativ große Datenmenge von bis zu 1,3 MB pro Bild, was die Einsetzbarkeit des Messgerätes zurzeit noch auf Forschungszwecke und kleinere klinische Untersuchungskollektive beschränkt.With rasterstereography, which was developed in the 80´s by Drerup & Hierholzer, a new method was developed which allows with the help of surface back analysis to supplement radiological and clinical examinations of the spine in orthopeadic and biomechanic questions. Based on the principal of triangulation it provides a quick, contact-free and large-sized analysis of the trunk posture. Therefor changes in light-line-patterns, which are projected by a slide projector on the back of the patient, are detected by a digital camera and reconstructed three-dimensionally. With the help of a personal-computer it is possible to calculate the spine posture out of the 3D-model. With the currently used measurement system it is only possible to measure under statical conditions. Because of that, aim of this present study was to evolve hard- and software-components to measure under dynamic conditions. To test the accuracy of the new system under dynamic conditions markers on a wodden plate were measured. The plate was therefor moved by a computer-controlled robotic-arm. Alltogether seven different movements of the plate were examined. The "trunk length" was measured with an accuracy of 3,29 mm and the "dimple distance" with an accuracy of 1,04 mm. To test the reliability of the system active sports women were tested repeatetly during still standing and during an arm-circle movement. As a result we got standard deviations (SD) between 1,92-7,52 mm for the "trunk length" and SD´s for the "trunk inclination" between 0,24-1,02°. Other tested parameters were measured with SD´s for the "kyphotic angle" from 0,82-1,79° and for the "lordotic angle" from 1,04-2,99°. Finally the modified Matthiass-Test was substantiated with the new measurement system. Therefor 31 acticve and healthy tennis-players have been evaluated. To create greater changes in the spine posture of the patients the test was accomplished with additional weights. The main focus was set on the changes of the posture at the beginning and at the end of the Matthiass-Test. With the help of of these examinations it was possible to show that during the test there was a slight increase in the "trunk length". Also an erection of the trunk was found, combined with a moderate decrease in the "kyphotic angle" and a small increase in the "lordotic angle". With the help of mathematical-correlation-tests it could be proved, that additional 5% of the body-weight are enough to bring out significant changes in the spine postures of healthy patients. Although these results must be veryfied with posture-weak patients. With the 4D-Imager a measurement system was developed to ensure precise, radiation-free, contact-free and dynamic examinations of spine postures. Unfortunately there a still some small irregulations in the automatic detection of the seventh vertebral body, which will have to get fixed. A limitation still is the maximum picure-frequency of 15 Hz, which limits the use of the system to slow to medium-fast movements. Also the relatively big data size of 1,3 Mb per picure limits the use of the system so far for trials and clinical examinations with a small collective

Outcomes, Return to Sport, and Failures of MPFL Reconstruction Using Autografts in Children and Adolescents with Recurrent Patellofemoral Instability: A Systematic Review

Introduction: This study systematically reviews and updates the current evidence on the outcomes of medial patellofemoral ligament (MPFL) reconstruction using autografts in children and adolescents with recurrent patellofemoral instability. The outcomes of interest were improvements in patient reported outcomes measures (PROMs), return to sport rates, and the rates of surgical failure. Methods: This systematic review was performed according to the 2020 PRISMA guidelines. The following electronic databases were accessed in October 2022: PubMed, Scopus, Web of Science. All the clinical studies which investigated the outcomes of MPFL reconstruction using autografts in children and adolescents with recurrent patellofemoral instability were accessed. Only studies which included patients younger than 18 years were considered. Techniques, case reports, guidelines, comments, editorials, letters, protocols, reviews, and meta-analyses were excluded. Studies which included patients with congenital or acute patellofemoral instability were not eligible, nor were those which focused exclusively on hyperlaxity. Results: Data from 477 patients (510 procedures) were retrieved. Of the patients, 41% (196 of 477) were women. The mean length of follow-up was 33.7 ± 28.8 months. The mean age of the patients was 14.6 ± 1.6 years. At the last follow-up, all PROMs of interest were statistically improved. The mean time to return to sport was 6.1 ± 1.1 months. Of the patients, 27% reduced their level of activity after surgical stabilization. A total of 87% of patients returned to practice sport. A total of 5% (26 of 477) and 2% (9 of 363) of patients experienced further dislocations and subluxations, respectively, during the follow-up period. Moreover, 4% (16 of 403) of patients underwent a further surgical procedure for patellofemoral instability within the follow-up period. Conclusion: MPFL reconstruction using autografts is effective in children and adolescents with recurrent patellofemoral instability

The Nintendo® Wii Fit Balance Board can be used as a portable and low-cost posturography system with good agreement compared to established systems

Background!#!Almost all epidemiological studies over the past 40 years have determined that the incidence of fragility fractures is increasing. Therefore, the assessment of postural stability and monitoring any progress during balance training for geriatric patients to prevent falls are becoming more important. The Nintendo!##!Methods!#!This prospective study analyzed the diagnostic value of the Wii Fit Balance Board in 41 healthy subjects using two measurements: the yoga task 'tree,' which is performed in one-leg stance; and the balance game 'table tilt.' Our investigation compared these tasks to two established, regularly used systems, the MFT-S3 Check and the Posturomed, by looking for correlation and agreement, using Bland-Altman plots, as well as for differences to demographic data. All measurement tools were also compared to the Sensory Organization Test-the gold standard for detecting impaired balance.!##!Results!#!We found a moderate correlation between the yoga exercise 'tree' and the Sensory Organization Test (correlation coefficient r = 0.514, p = 0.001) as well as the MFT-S3 Check (r = 0.356-0.472, p = 0.002-0.022) and the Posturomed (r = 0.345, p = 0.027). However, results from the balance game 'table tilt' did not show a significant correlation with those of the systems to which we compared it (p = 0.301-0.953).!##!Conclusions!#!According to the literature, the raw data from the Wii Fit Balance Board are comparable to that obtained by laboratory-grade force platforms. We have found, however, that the yoga pose 'tree,' as integrated into the Nintendo!##!Level of evidence!#!2b

Spinal posture and pelvic position in three hundred forty-five elementary school children: a rasterstereographic pilot study

Children’s posture has been of growing concern due to observations that it seems to be impaired compared to previous generations. So far there is no reference data for spinal posture and pelvic position in healthy children available. Purpose of this pilot study was to determine rasterstereographic posture values in children during their second growth phase. Three hundred and forty-five pupils were measured with a rasterstereographic device in a neutral standing position with hanging arms. To further analyse for changes in spinal posture during growth, the children were divided into 12-month age clusters. A mean kyphotic angle of 47.1°±7.5 and a mean lordotic angle of 42.1°±9.9 were measured. Trunk imbalance in girls (5.85 mm±0.74) and boys (7.48 mm± 0.83) varied only little between the age groups, with boys showing slightly higher values than girls. The trunk inclination did not show any significant differences between the age groups in boys or girls. Girls’ inclination was 2.53°±1.96 with a tendency to decreasing angles by age, therefore slightly smaller compared to boys (2.98°±2.18). Lateral deviation (4.8 mm) and pelvic position (tilt: 2.75 mm; torsion: 1.53°; inclination: 19.8°±19.8) were comparable for all age groups and genders. This study provides the first systematic rasterstereographic analysis of spinal posture in children between 6 and 11 years. With the method of rasterstereography a reliable three-dimensional analysis of spinal posture and pelvic position is possible. Spinal posture and pelvic position does not change significantly with increasing age in this collective of children during the second growth phase