121 research outputs found
Characteristic Energy Losses with High Energy Electrons up to 2.5 MeV
Some aspects of the influence of the energy of the incident electrons in electron energy loss spectroscopy (EELS) are considered. It is shown that this method of analysis used in high voltage electron microscopy, permits one to observe, with a better edge jump ratio than at lower accelerating voltages, the characteristic edges. One important question is to eliminate artefacts in the counting and to record only electrons from the true spectrum. Some recent examples are given. One of them concerns extended energy loss fine structures (EXELFS). It seems high voltage electron microscopy (HVEM) could be very useful in this domain
Hydration properties of the lumbar intervertebral discs in AIS after surgical correction:five years follow-up and comparison with an age-matched control group
We compared disc hydration properties of adolescent idiopathic scoliosis before and 5 years after spinal fusion with an age-matched control group. We conducted a prospective MRI follow-up of 23 patients. Disc and nucleus volumes were reconstructed on T2 weighted sequence. In the scoliotic group, vd and vn were lower than control group, hydration ratio (Vn/Vd) was lower. After surgery, subjacent discs rehydrated. AIS induces a loss of IVD hydration. Surgical correction can reverse homeostasis disturbances related to spinal deformity
Post mortem magnetic resonance imaging in the fetus, infant and child: A comparative study with conventional autopsy (MaRIAS Protocol)
<p>Abstract</p> <p>Background</p> <p>Minimally invasive autopsy by post mortem magnetic resonance (MR) imaging has been suggested as an alternative for conventional autopsy in view of the declining consented autopsy rates. However, large prospective studies rigorously evaluating the accuracy of such an approach are lacking. We intend to compare the accuracy of a minimally invasive autopsy approach using post mortem MR imaging with that of conventional autopsy in fetuses, newborns and children for detection of the major pathological abnormalities and/or determination of the cause of death.</p> <p>Methods/Design</p> <p>We recruited 400 consecutive fetuses, newborns and children referred for conventional autopsy to one of the two participating hospitals over a three-year period. We acquired whole body post mortem MR imaging using a 1.5 T MR scanner (Avanto, Siemens Medical Solutions, Enlargen, Germany) prior to autopsy. The total scan time varied between 90 to 120 minutes. Each MR image was reported by a team of four specialist radiologists (paediatric neuroradiology, paediatric cardiology, paediatric chest & abdominal imaging and musculoskeletal imaging), blinded to the autopsy data. Conventional autopsy was performed according to the guidelines set down by the Royal College of Pathologists (UK) by experienced paediatric or perinatal pathologists, blinded to the MR data. The MR and autopsy data were recorded using predefined categorical variables by an independent person.</p> <p>Discussion</p> <p>Using conventional post mortem as the gold standard comparator, the MR images will be assessed for accuracy of the anatomical morphology, associated lesions, clinical usefulness of information and determination of the cause of death. The sensitivities, specificities and predictive values of post mortem MR alone and MR imaging along with other minimally invasive post mortem investigations will be presented for the final diagnosis, broad diagnostic categories and for specific diagnosis of each system.</p> <p>Clinical Trial Registration</p> <p><a href="http://www.clinicaltrials.gov/ct2/show/NCT01417962">NCT01417962</a></p> <p><b>NIHR Portfolio Number: </b>6794</p
Conception et développement d'un dispositif de protection ultime de données à base de nanothermites déposées par impression 3D
Security has become an essential element of electronic systems used in the storage of data personal or banking data or in critical equipment such as military systems, embedded systems or energy infrastructures. Indeed, electronic systems increasingly handle sensitive data in uncontrolled environments and are faced with sabotage attacks, industrial espionage or reverse engineering. Given the increasing number of attacks over the past decade, it is crucial to harden technologies and develop micro-security capable of protecting sensitive data as well as preventing physical intrusion. This thesis falls into this context, by proposing a new concept of ultimate security consisting in placing on the sensitive component, a device capable of very quickly and reliably destroying the component containing the sensitive data in the event of an intrusion. Our concept and the resulting device, called ultimate security device (USD), is activated by a reactive composite material based on an Al/CuO nanothermite whose very energetic reaction destroys the chip containing the sensitive data in less than 100 µs. In this thesis we first developed a pyroMEMS to initiate in less than 30 µs the reactive composite material based on nanothermite, and proposed an alternative version which does not initiate under 1 A / 1 W for 5 min thus respecting the STANAG standardization in effect in some applications. We have designed and shaped a reactive ink based on Al/CuO nanopowder and copper complex that can be deposited by 3D printing on electronic circuits. After studying the stabilization of this ink with a polymer, the PVP, (wt% = 5%) we have not only developed a syringe-driver deposition equipment but also characterized in initiation and combustion the layers of reactive composite material thus deposited. My thesis ended with the realization of several prototypes of the USD component, their characterization, validating the feasibility of our security concept. During this thesis, I was also able to deepen the knowledge on the initiation of Al/CuO multilayer nanothermites, highlighting that the initiation in these stacks of thin layers, comprising a semiconductor oxide, CuO, is not only due to the Joule effect. I was finally able to optimize an electronic ignition of the pyroMEMS by capacitive discharge allowing reliable and very fast initiations (µs).La sĂ©curitĂ© est devenue un Ă©lĂ©ment essentiel des systèmes Ă©lectroniques utilisĂ©s dans le stockage de donnĂ©es personnelles, bancaires ou dans des Ă©quipements critiques tels que les systèmes militaires, systèmes embarquĂ©s ou les infrastructures Ă©nergĂ©tiques. En effet, les systèmes Ă©lectroniques manipulent de plus en plus des donnĂ©es sensibles dans des environnements non contrĂ´lĂ©s et sont confrontĂ©s Ă des attaques de sabotage, de l'espionnage industriel ou du rĂ©tro engineering. Compte tenu du nombre croissant d'attaques au cours de la dernière dĂ©cennie, il est crucial de durcir les technologies et dĂ©velopper des micro-sĂ©curitĂ©s capables de protĂ©ger les donnĂ©es sensibles ainsi qu'empĂŞcher l'intrusion physique. Cette thèse rentre dans ce contexte, en proposant un nouveau concept de sĂ©curitĂ© ultime consistant Ă placer sur le composant sensible, un dispositif capable de dĂ©truire de façon très rapide et fiable le composant contenant les donnĂ©es sensibles en cas de d'intrusion. Notre concept et le dispositif en dĂ©coulant, appelĂ© dispositif de sĂ©curitĂ© ultime (USD), est actionnĂ© par un matĂ©riau composite rĂ©actif Ă base d'une nanothermite Al/CuO dont la rĂ©action très Ă©nergĂ©tique dĂ©truit en moins de 100 µs la puce contenant les donnĂ©es sensibles. Dans cette thèse nous avons d'abord dĂ©veloppĂ© un pyroMEMS pour initier en moins de 30 μs le matĂ©riau composite rĂ©actif Ă base de nanothermite, et avons proposĂ© une version alternative qui ne s'initie pas sous 1A / 1W pendant 5 min respectant ainsi les rĂ©glementations STANAG en vigueur dans certaines applications. Nous avons conçu et mis en forme une encre rĂ©active Ă base de nanopoudre Al/CuO et de complexe de cuivre dĂ©posable par impression 3D sur des circuits Ă©lectroniques. Après avoir Ă©tudiĂ© la stabilisation de cette encre avec un polymère PVP (wt% = 5%) nous avons non seulement mis au point un Ă©quipement de dĂ©pĂ´t par pousse seringue mais aussi caractĂ©risĂ© en initiation et combustion les couches de matĂ©riau composite rĂ©actif ainsi dĂ©posĂ©. Ma thèse s'est conclue avec la rĂ©alisation de plusieurs prototypes du composant USD, leur caractĂ©risation, validant ainsi l'Ă©tape de faisabilitĂ© de notre concept de sĂ©curitĂ©. Au cours de cette thèse, j'ai pu aussi approfondir les connaissances sur l'initiation des nanothermites multicouches Al/CuO, mettant en Ă©vidence que l'initiation dans ces empilements de couches minces, comprenant un oxyde semi-conducteur, le CuO, n'est pas que le fait de l'effet Joule. J'ai enfin pu alors optimiser une Ă©lectronique d'allumage du pyroMEMS par dĂ©charge capacitive permettant des initiations fiables et très rapides (µs)
Conception et développement d'un dispositif de protection ultime de données à base de nanothermites déposées par impression 3D
Security has become an essential element of electronic systems used in the storage of data personal or banking data or in critical equipment such as military systems, embedded systems or energy infrastructures. Indeed, electronic systems increasingly handle sensitive data in uncontrolled environments and are faced with sabotage attacks, industrial espionage or reverse engineering. Given the increasing number of attacks over the past decade, it is crucial to harden technologies and develop micro-security capable of protecting sensitive data as well as preventing physical intrusion. This thesis falls into this context, by proposing a new concept of ultimate security consisting in placing on the sensitive component, a device capable of very quickly and reliably destroying the component containing the sensitive data in the event of an intrusion. Our concept and the resulting device, called ultimate security device (USD), is activated by a reactive composite material based on an Al/CuO nanothermite whose very energetic reaction destroys the chip containing the sensitive data in less than 100 µs. In this thesis we first developed a pyroMEMS to initiate in less than 30 µs the reactive composite material based on nanothermite, and proposed an alternative version which does not initiate under 1 A / 1 W for 5 min thus respecting the STANAG standardization in effect in some applications. We have designed and shaped a reactive ink based on Al/CuO nanopowder and copper complex that can be deposited by 3D printing on electronic circuits. After studying the stabilization of this ink with a polymer, the PVP, (wt% = 5%) we have not only developed a syringe-driver deposition equipment but also characterized in initiation and combustion the layers of reactive composite material thus deposited. My thesis ended with the realization of several prototypes of the USD component, their characterization, validating the feasibility of our security concept. During this thesis, I was also able to deepen the knowledge on the initiation of Al/CuO multilayer nanothermites, highlighting that the initiation in these stacks of thin layers, comprising a semiconductor oxide, CuO, is not only due to the Joule effect. I was finally able to optimize an electronic ignition of the pyroMEMS by capacitive discharge allowing reliable and very fast initiations (µs).La sĂ©curitĂ© est devenue un Ă©lĂ©ment essentiel des systèmes Ă©lectroniques utilisĂ©s dans le stockage de donnĂ©es personnelles, bancaires ou dans des Ă©quipements critiques tels que les systèmes militaires, systèmes embarquĂ©s ou les infrastructures Ă©nergĂ©tiques. En effet, les systèmes Ă©lectroniques manipulent de plus en plus des donnĂ©es sensibles dans des environnements non contrĂ´lĂ©s et sont confrontĂ©s Ă des attaques de sabotage, de l'espionnage industriel ou du rĂ©tro engineering. Compte tenu du nombre croissant d'attaques au cours de la dernière dĂ©cennie, il est crucial de durcir les technologies et dĂ©velopper des micro-sĂ©curitĂ©s capables de protĂ©ger les donnĂ©es sensibles ainsi qu'empĂŞcher l'intrusion physique. Cette thèse rentre dans ce contexte, en proposant un nouveau concept de sĂ©curitĂ© ultime consistant Ă placer sur le composant sensible, un dispositif capable de dĂ©truire de façon très rapide et fiable le composant contenant les donnĂ©es sensibles en cas de d'intrusion. Notre concept et le dispositif en dĂ©coulant, appelĂ© dispositif de sĂ©curitĂ© ultime (USD), est actionnĂ© par un matĂ©riau composite rĂ©actif Ă base d'une nanothermite Al/CuO dont la rĂ©action très Ă©nergĂ©tique dĂ©truit en moins de 100 µs la puce contenant les donnĂ©es sensibles. Dans cette thèse nous avons d'abord dĂ©veloppĂ© un pyroMEMS pour initier en moins de 30 μs le matĂ©riau composite rĂ©actif Ă base de nanothermite, et avons proposĂ© une version alternative qui ne s'initie pas sous 1A / 1W pendant 5 min respectant ainsi les rĂ©glementations STANAG en vigueur dans certaines applications. Nous avons conçu et mis en forme une encre rĂ©active Ă base de nanopoudre Al/CuO et de complexe de cuivre dĂ©posable par impression 3D sur des circuits Ă©lectroniques. Après avoir Ă©tudiĂ© la stabilisation de cette encre avec un polymère PVP (wt% = 5%) nous avons non seulement mis au point un Ă©quipement de dĂ©pĂ´t par pousse seringue mais aussi caractĂ©risĂ© en initiation et combustion les couches de matĂ©riau composite rĂ©actif ainsi dĂ©posĂ©. Ma thèse s'est conclue avec la rĂ©alisation de plusieurs prototypes du composant USD, leur caractĂ©risation, validant ainsi l'Ă©tape de faisabilitĂ© de notre concept de sĂ©curitĂ©. Au cours de cette thèse, j'ai pu aussi approfondir les connaissances sur l'initiation des nanothermites multicouches Al/CuO, mettant en Ă©vidence que l'initiation dans ces empilements de couches minces, comprenant un oxyde semi-conducteur, le CuO, n'est pas que le fait de l'effet Joule. J'ai enfin pu alors optimiser une Ă©lectronique d'allumage du pyroMEMS par dĂ©charge capacitive permettant des initiations fiables et très rapides (µs)
Design and development of an ultimate data protection device based on nanothermites deposited by 3D printing
La sĂ©curitĂ© est devenue un Ă©lĂ©ment essentiel des systèmes Ă©lectroniques utilisĂ©s dans le stockage de donnĂ©es personnelles, bancaires ou dans des Ă©quipements critiques tels que les systèmes militaires, systèmes embarquĂ©s ou les infrastructures Ă©nergĂ©tiques. En effet, les systèmes Ă©lectroniques manipulent de plus en plus des donnĂ©es sensibles dans des environnements non contrĂ´lĂ©s et sont confrontĂ©s Ă des attaques de sabotage, de l'espionnage industriel ou du rĂ©tro engineering. Compte tenu du nombre croissant d'attaques au cours de la dernière dĂ©cennie, il est crucial de durcir les technologies et dĂ©velopper des micro-sĂ©curitĂ©s capables de protĂ©ger les donnĂ©es sensibles ainsi qu'empĂŞcher l'intrusion physique. Cette thèse rentre dans ce contexte, en proposant un nouveau concept de sĂ©curitĂ© ultime consistant Ă placer sur le composant sensible, un dispositif capable de dĂ©truire de façon très rapide et fiable le composant contenant les donnĂ©es sensibles en cas de d'intrusion. Notre concept et le dispositif en dĂ©coulant, appelĂ© dispositif de sĂ©curitĂ© ultime (USD), est actionnĂ© par un matĂ©riau composite rĂ©actif Ă base d'une nanothermite Al/CuO dont la rĂ©action très Ă©nergĂ©tique dĂ©truit en moins de 100 µs la puce contenant les donnĂ©es sensibles. Dans cette thèse nous avons d'abord dĂ©veloppĂ© un pyroMEMS pour initier en moins de 30 μs le matĂ©riau composite rĂ©actif Ă base de nanothermite, et avons proposĂ© une version alternative qui ne s'initie pas sous 1A / 1W pendant 5 min respectant ainsi les rĂ©glementations STANAG en vigueur dans certaines applications. Nous avons conçu et mis en forme une encre rĂ©active Ă base de nanopoudre Al/CuO et de complexe de cuivre dĂ©posable par impression 3D sur des circuits Ă©lectroniques. Après avoir Ă©tudiĂ© la stabilisation de cette encre avec un polymère PVP (wt% = 5%) nous avons non seulement mis au point un Ă©quipement de dĂ©pĂ´t par pousse seringue mais aussi caractĂ©risĂ© en initiation et combustion les couches de matĂ©riau composite rĂ©actif ainsi dĂ©posĂ©. Ma thèse s'est conclue avec la rĂ©alisation de plusieurs prototypes du composant USD, leur caractĂ©risation, validant ainsi l'Ă©tape de faisabilitĂ© de notre concept de sĂ©curitĂ©. Au cours de cette thèse, j'ai pu aussi approfondir les connaissances sur l'initiation des nanothermites multicouches Al/CuO, mettant en Ă©vidence que l'initiation dans ces empilements de couches minces, comprenant un oxyde semi-conducteur, le CuO, n'est pas que le fait de l'effet Joule. J'ai enfin pu alors optimiser une Ă©lectronique d'allumage du pyroMEMS par dĂ©charge capacitive permettant des initiations fiables et très rapides (µs).Security has become an essential element of electronic systems used in the storage of data personal or banking data or in critical equipment such as military systems, embedded systems or energy infrastructures. Indeed, electronic systems increasingly handle sensitive data in uncontrolled environments and are faced with sabotage attacks, industrial espionage or reverse engineering. Given the increasing number of attacks over the past decade, it is crucial to harden technologies and develop micro-security capable of protecting sensitive data as well as preventing physical intrusion. This thesis falls into this context, by proposing a new concept of ultimate security consisting in placing on the sensitive component, a device capable of very quickly and reliably destroying the component containing the sensitive data in the event of an intrusion. Our concept and the resulting device, called ultimate security device (USD), is activated by a reactive composite material based on an Al/CuO nanothermite whose very energetic reaction destroys the chip containing the sensitive data in less than 100 µs. In this thesis we first developed a pyroMEMS to initiate in less than 30 µs the reactive composite material based on nanothermite, and proposed an alternative version which does not initiate under 1 A / 1 W for 5 min thus respecting the STANAG standardization in effect in some applications. We have designed and shaped a reactive ink based on Al/CuO nanopowder and copper complex that can be deposited by 3D printing on electronic circuits. After studying the stabilization of this ink with a polymer, the PVP, (wt% = 5%) we have not only developed a syringe-driver deposition equipment but also characterized in initiation and combustion the layers of reactive composite material thus deposited. My thesis ended with the realization of several prototypes of the USD component, their characterization, validating the feasibility of our security concept. During this thesis, I was also able to deepen the knowledge on the initiation of Al/CuO multilayer nanothermites, highlighting that the initiation in these stacks of thin layers, comprising a semiconductor oxide, CuO, is not only due to the Joule effect. I was finally able to optimize an electronic ignition of the pyroMEMS by capacitive discharge allowing reliable and very fast initiations (µs)
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