Non-invasive monitoring of diaphragmatic timing by means of surface contact sensors: an experimental study in dogs

Background: Non-invasive monitoring of respiratory muscle function is an area of increasing research interest, resulting in the appearance of new monitoring devices, one of these being piezoelectric contact sensors. The present study was designed to test whether the use of piezoelectric contact (non-invasive) sensors could be useful in respiratory monitoring, in particular in measuring the timing of diaphragmatic contraction.Methods: Experiments were performed in an animal model: three pentobarbital anesthetized mongrel dogs. The motion of the thoracic cage was acquired by means of a piezoelectric contact sensor placed on the costal wall. This signal is compared with direct measurements of the diaphragmatic muscle length, made by sonomicrometry. Furthermore, to assess the diaphragmatic function other respiratory signals were acquired: respiratory airflow and transdiaphragmatic pressure. Diaphragm contraction time was estimated with these four signals. Using diaphragm length signal as reference, contraction times estimated with the other three signals were compared with the contraction time estimated with diaphragm length signal.Results: The contraction time estimated with the TM signal tends to give a reading 0.06 seconds lower than the measure made with the DL signal (-0.21 and 0.00 for FL and DP signals, respectively), with a standard deviation of 0.05 seconds (0.08 and 0.06 for FL and DP signals, respectively). Correlation coefficients indicated a close link between time contraction estimated with TM signal and contraction time estimated with DL signal (a Pearson correlation coefficient of 0.98, a reliability coefficient of 0.95, a slope of 1.01 and a Spearman's rank-order coefficient of 0.98). In general, correlation coefficients and mean and standard deviation of the difference were better in the inspiratory load respiratory test than in spontaneous ventilation tests.Conclusion: The technique presented in this work provides a non-invasive method to assess the timing of diaphragmatic contraction in canines, using a piezoelectric contact sensor placed on the costal wall.

SMART News, Summer 2006

News from the Iowa Careers Consortium

Assinatura Digital Foco Smart Card

A assinatura digital é um processo de assinatura electrónica baseado no sistema criptográfico assimétrico composto por um algoritmo ou série de algoritmos, mediante o qual é gerado um par de chaves assimétricas exclusivas e complementares. Tal como a assinatura manuscrita, a assinatura digital não pode ser falsificada, pelo que se adiciona uma função hash ao valor da chave gerada, para garantir a segurança do sistema. A assinatura digital permite, ao mesmo tempo, a identificação positiva do autor de uma mensagem (ou do signatário de um documento) e a verificação da integridade da mesma. Refira-se, porém, que a assinatura digital pode ser anexa a qualquer mensagem, seja esta decifrada ou não, apenas para que o receptor tenha a certeza da identidade do emissor e de que a mensagem chegou intacta ao destino. Baseia-se na criptografia da chave pública, que usa um algoritmo de duas chaves, a privada e a pública, diferentes mas matematicamente associadas: a primeira cria a assinatura digital e decifra os dados; a segunda verifica a assinatura e devolve-a ao formato original. O autor da mensagem mantém secreta a sua chave privada e divulga a chave pública, e vice-versa. A identidade do dono da chave pública é atestada pelo certificado digital emitido por uma entidade certificadora (uma espécie de notário). Independentemente da forma que assume, a assinatura electrónica, e a digital em particular, deve cumprir três funções: a autenticação (tal como acontece com o habitual gatafunho a que chamamos assinatura, apenas o indivíduo deve ser capaz de a reproduzir); não repudiação (quando o indivíduo assina não pode voltar atrás); e integridade (é necessário assegurar que os documentos assinados não são alterados sem o consentimento dos signatários).

Front-Crawl propulsive phase detection using inertial sensors

Front crawl is an alternating swimming stroke technique in which different phases of arm movement induce changes in acceleration of limbs and body. This study proposes a new approach to use inertial body worn sensors to estimate main temporal phases of front crawl. Distinctive features in kinematic signals are used to detect the temporal phases. These temporal phases are key information sources of qualitative and quantitative evaluation of swimming coordination, which have been assessed previously by video analysis. The present method has been evaluated upon a wide range of coordination and showed a difference of 4.9% with video based system. The results are in line with video analysis inter-operator variability yet offering an easy-to-use system for trainers.

Quantitative estimation of foot-flat and stance phase of gait using foot-worn inertial sensors.

Time periods composing stance phase of gait can be clinically meaningful parameters to reveal differences between normal and pathological gait. This study aimed, first, to describe a novel method for detecting stance and inner-stance temporal events based on foot-worn inertial sensors; second, to extract and validate relevant metrics from those events; and third, to investigate their suitability as clinical outcome for gait evaluations. 42 subjects including healthy subjects and patients before and after surgical treatments for ankle osteoarthritis performed 50-m walking trials while wearing foot-worn inertial sensors and pressure insoles as a reference system. Several hypotheses were evaluated to detect heel-strike, toe-strike, heel-off, and toe-off based on kinematic features. Detected events were compared with the reference system on 3193 gait cycles and showed good accuracy and precision. Absolute and relative stance periods, namely loading response, foot-flat, and push-off were then estimated, validated, and compared statistically between populations. Besides significant differences observed in stance duration, the analysis revealed differing tendencies with notably a shorter foot-flat in healthy subjects. The result indicated which features in inertial sensors' signals should be preferred for detecting precisely and accurately temporal events against a reference standard. The system is suitable for clinical evaluations and provides temporal analysis of gait beyond the common swing/stance decomposition, through a quantitative estimation of inner-stance phases such as foot-flat.

Estudi del procès evolutiu de la maduració del raïm mitjançant un sistema de sensors de temperatura i humitat

Treball de recerca realitzat per alumnes d’ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l’any 2010. L’objectiu principal d'aquest treball és analitzar i quantificar la relació i influència que podria existir entre alguns paràmetres que defineixen les condicions meteorològiques i l'estat de maduració del raïm en les setmanes prèvies a la verema. En la part introductòria s'estableixen els fonaments biològics i tecnològics, per donar pas a la secció on es duu a terme la implantació tecnològica, i s'explica la metodologia experimental i analítica seguides, per donar lloc a l'anàlisi, estudi i valoració dels resultats obtinguts. En el fons, i al llarg de tot el treball de recerca, es pretén que el lector encuriosit es vegi motivat per extreure les seves pròpies deduccions, conclusions i formular els seus propis dubtes sobre els procediments que es descriuen, així com els resultats finals. S'ha pogut establir a partir dels resultats empírics una equació matemàtica entre l'increment de la concentració dels sucres del raïm (factor principal en la seva maduració) i el nombre d'hores de Sol acumulades.

Una Red de Sensores para las Smart Cities

El objetivo del trabajo fin de Master consiste en el estudio de redes de sensores inalámbricos para las Smart Cities. En particular, se implementa una red inalámbrica (tecnología ZIGBEE como protocolo de comunicación inalámbrica con micrófonos como sensores, para recolectar niveles de ruido. Hemos elegido el Arduino como plataforma de cálculo para controlar cada nodo, y XBee como módulos de comunicación inalámbrico. La red sensorial cuenta con tres nodos sensores que capturan el ruido y lo envían a un nodo receptor, que hace de estación central encargado de monitorizar los niveles de ruido. Dicho coordinador está conectado mediante USB a un PC, donde podemos comprobar las medidas recibidas por el XBee. Finalmente estos datos se muestran en una interfaz gráfica en el computador conectado al coordinador. De esta forma, puede monitorizarse el nivel de ruido de tres lugares diferentes en tiempo real.

Non-invasive RF built-in testing using on-chip temperature sensors

This poster shows how to efficiently observe high-frequency figures of merit in RF circuits by measuring DC temperature with CMOS-compatible built-in sensors.

Artificial Urinary Sphincter based on smart materials

Objective: There are only a few established artificial urinary sphincters for treatment of incontinence. We have developed a new device composed by three parts: the actuator, three contractile rings and a control unit. The actuator is made of Nitinol fibers, driven by microprocessor. The fibers are linked to the rings placed around the urethra. They function with alternance in their open and closed position. This concept is called piano concept. With this set-up, the constant compression on the urethra is strongly reduced. Methods: Six male sheep have been used for this study. The sphincter was open each hour for a period of 10 min., to guaranty urination. The bladder was filled with water while one cuff was closed and bladder pressure was monitored. The animals were sacrificed. Two biopsies around two cuffs of each explant and all three cuffs from each explant including urethra were analyzed. Urethra not surrounded by a cuff was taken as control. Results: The pressure exerted by the sphincter around the urethra provided continence. Simulated incontinence occurred at a pressure of 1bar measured on the bladder wall using a pressure probe. The closing force of the cuff was approx. 0·7N. No difference in tissue structure and organization of the urethra with and without artificial sphincter was observed. Conclusions: This device has several advantages compared to other urinary sphincters. It is easy to implant, has no hydraulic nature and reduces ischemic injury of the urethra by the alternance of urethral part compressed. Proof of concept in vivo has been demonstrated. Other studies are planned to determine long-term outcome.

Software per al cronometratge de temps mitjançant sensors digitals

L’Slot, conegut per tots amb el nom d’Scalextric, s’ha implantat com a una forma d’oci habitual, la pràctica del qual no queda restringida als més petits, sinó que cada vegada crea més afició entre els grans. El fet que l’Slot s’hagi extès entre els adults n’ha revolucionat la pràctica. L’entrada al mercat de l’Slot de gent adulta, i amb poder adquisitiu molt superior als adolescents, ha provocat que les marques especialitzades vagin evolucionant els seus productes cada vegada més. Totes les marques s’han vist obligades a desenvolupar vehicles més competitius i alhora treure al mercat accessoris que augmentin la realitat del joc. Una de les necessitats que s’ha creat és la de competir entre jugadors. Aquesta competició tan pot ser en forma de carrera entre diversos participants, com de forma individual, cronometrant el temps de cada participant en un circuit. L’objectiu principal del projecte és crear un sistema capaç de realitzar cronometratges en temps real mitjançant sensors digitals ja existents en el mercat de l’Slot i poder controlar i visualitzar la informació des d’un PC. Per a poder captar els senyals dels sensors s’ha utilitzat un sistema microcontrolat, que garanteix gran velocitat d’adquisició, processament de dades i transmissió. La comunicació del Microcontrolador amb el PC s’ha realizat mitjançant el bus USB. El PC serà el controlador del sistema i donarà les ordres al Microcontrolador, podent així tenir control total sobre el funcionament del programa. També serà el PC el que tractarà els crocometratges enregistrats i els mostrarà per pantalla

Regulation of glucagon secretion by glucose transporter type 2 (glut2) and astrocyte-dependent glucose sensors.

Ripglut1;glut2-/- mice have no endogenous glucose transporter type 2 (glut2) gene expression but rescue glucose-regulated insulin secretion. Control of glucagon plasma levels is, however, abnormal, with fed hyperglucagonemia and insensitivity to physiological hypo- or hyperglycemia, indicating that GLUT2-dependent sensors control glucagon secretion. Here, we evaluated whether these sensors were located centrally and whether GLUT2 was expressed in glial cells or in neurons. We showed that ripglut1;glut2-/- mice failed to increase plasma glucagon levels following glucoprivation induced either by i.p. or intracerebroventricular 2-deoxy-D-glucose injections. This was accompanied by failure of 2-deoxy-D-glucose injections to activate c-Fos-like immunoreactivity in the nucleus of the tractus solitarius and the dorsal motor nucleus of the vagus. When glut2 was expressed by transgenesis in glial cells but not in neurons of ripglut1;glut2-/- mice, stimulated glucagon secretion was restored as was c-Fos-like immunoreactive labeling in the brainstem. When ripglut1;glut2-/- mice were backcrossed into the C57BL/6 genetic background, fed plasma glucagon levels were also elevated due to abnormal autonomic input to the alpha cells; glucagon secretion was, however, stimulated by hypoglycemic stimuli to levels similar to those in control mice. These studies identify the existence of central glucose sensors requiring glut2 expression in glial cells and therefore functional coupling between glial cells and neurons. These sensors may be activated at different glycemic levels depending on the genetic background.

A system to measure the kinematics during the entire ski jump sequence using inertial sensors.

Three-dimensional analysis of the entire sequence in ski jumping is recommended when studying the kinematics or evaluating performance. Camera-based systems which allow three-dimensional kinematics measurement are complex to set-up and require extensive post-processing, usually limiting ski jumping analyses to small numbers of jumps. In this study, a simple method using a wearable inertial sensors-based system is described to measure the orientation of the lower-body segments (sacrum, thighs, shanks) and skis during the entire jump sequence. This new method combines the fusion of inertial signals and biomechanical constraints of ski jumping. Its performance was evaluated in terms of validity and sensitivity to different performances based on 22 athletes monitored during daily training. The validity of the method was assessed by comparing the inclination of the ski and the slope at landing point and reported an error of -0.2±4.8°. The validity was also assessed by comparison of characteristic angles obtained with the proposed system and reference values in the literature; the differences were smaller than 6° for 75% of the angles and smaller than 15° for 90% of the angles. The sensitivity to different performances was evaluated by comparing the angles between two groups of athletes with different jump lengths and by assessing the association between angles and jump lengths. The differences of technique observed between athletes and the associations with jumps length agreed with the literature. In conclusion, these results suggest that this system is a promising tool for a generalization of three-dimensional kinematics analysis in ski jumping.

Web semàntica aplicada a la gestió i caracterització de dades, sensors i accés a serveis per a vaixells d'investigació oceanogràfica

Amb el present projecte es proposa fer un estudi de la web semàntica aplicada a la descripció i modelització de la instrumentació marina operada en el context de campanyes d'investigació oceanogràfica.

Heel and toe clearance estimation for gait analysis using wireless inertial sensors.

Tripping is considered a major cause of fall in older people. Therefore, foot clearance (i.e., height of the foot above ground during swing phase) could be a key factor to better understand the complex relationship between gait and falls. This paper presents a new method to estimate clearance using a foot-worn and wireless inertial sensor system. The method relies on the computation of foot orientation and trajectory from sensors signal data fusion, combined with the temporal detection of toe-off and heel-strike events. Based on a kinematic model that automatically estimates sensor position relative to the foot, heel and toe trajectories are estimated. 2-D and 3-D models are presented with different solving approaches, and validated against an optical motion capture system on 12 healthy adults performing short walking trials at self-selected, slow, and fast speed. Parameters corresponding to local minimum and maximum of heel and toe clearance were extracted and showed accuracy ± precision of 4.1 ± 2.3 cm for maximal heel clearance and 1.3 ± 0.9 cm for minimal toe clearance compared to the reference. The system is lightweight, wireless, easy to wear and to use, and provide a new and useful tool for routine clinical assessment of gait outside a dedicated laboratory.