Destructive quantum interference effect is implemented in large area molecular junctions to improve signatures of electron-phonon interaction. Vertical molecular junctions based on a cross-conjugated ...anthraquinone layer were fabricated and low-noise transport measurements were performed by acquiring simultaneously the current-voltage characteristics, its second derivative, and the differential conductance. Signatures of vibrational modes excited by inelastic events are present in the whole measured voltage range and superpose to the conductance suppression induced by destructive quantum interference. As a consequence vibrational modes have improved visibility in the low energy window (<80meV). Inelastic electron transport spectroscopy data are compared to infrared attenuated total reflection spectroscopy on Au/anthraquinone thin films. Common vibrational modes can be clearly identified, but inelastic electron tunneling spectroscopy reveals the existence of vibrational modes in a wider energy range (0–400meV) where infrared spectroscopy is lacking.
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A key issue to push molecular devices toward a new range of applications is the ability to master large scale integration while preserving the device’s functionality. Furthermore, providing extra ...tunability of the device by external parameters, such as gating in a transistor-like configuration, is highly suited for molecular electronics. Large area molecular junctions in crossbar geometry have demonstrated high yields and compatible and compatible fabrication with Complementary Metal Oxide Semiconductor (CMOS) technology. However, such a device’s geometry favors diffusion of metallic atoms in the molecular layer and gives a very limited access to perform electrical or optical gating on molecules. In this work, we propose a new molecular junction architecture going behind these limits. We report a robust approach for the fabrication of molecular junctions based on the electrografting of a nanometer-thick molecular layer in high aspect ratio metallic nanotrenches. Nanotrenches are obtained by edge-mediated shadow deposition, resulting in laterally aligned electrodes with a 10.3 nm ± 3.3 nm average spacing along a 20 μm length. An in-solution electroreduction of diazonium salts is subsequently performed to fill the nanotrenches by a thin oligomeric layer of anthraquinone molecules. Electronic transport measurements performed at room temperature reveal the ability to produce stable molecular devices. Such a new junction’s engineering offers the key advantages of high fabrication yield, great amenability for compact assembly, and reduced leakage current. The proposed architecture opens interesting perspectives to investigate fundamental and applied questions in molecular electronics, in which coupling of the molecules with external stimuli is required.
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4.
Syria at the Crossroads Salhani, Claude
Middle East policy,
09/2003, Volume:
10, Issue:
3
Journal Article
Peer reviewed
With the regime change Iraq now a reality, the natural course of action for the Bush administration seemed to focus on the next phase of its Middle East initiative: pacifying Syria and eradicating ...terrorism. Salhani asserts that for peace to hold, it is imperative to incorporate all the pieces of the complicated Mideast mosaic simultaneously.
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BFBNIB, CEKLJ, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, ODKLJ, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Lassociation de tumeurs primitives synchrones a un cancer colorectal a fait lobjet de plusieurs publications. Elle peut survenir de maniere sporadique ou rentrer dans le cadre de syndromes cliniques ...bien definis tel que le syndrome de Lynch. Il sagit dune entite clinique rare mais reelle, dont lincidence est variable. La decouverte du carcinome renale est le plus souvent fortuite au cours du bilan dextension. Letiopathogenie nest pas completement elucidee incluant des facteurs de risques genetiques et environnementaux. Le traitement se base essentiellement sur la resection chirurgical generalement dans un seul temps, mais la decision doit être prise dans une reunion de concertation pluridisciplinaire. Letude genetique savere necessaire pour mieux elucider letiopathogenie. Nous rapportons le cas dun homme age de 52 ans qui a simultanement presente un adenocarcinome colique et un carcinome a cellules claires renales, de decouverte fortuite au cours du bilan dextension du carcinome colorectal. Nous discuterons la pathogenie ainsi que le pronostic et le traitement de cette entite rarement decrite.
La necrose aigue de lœsophage, egalement appelee œsophage noir est une forme grave et rare de lesion œsophagienne qui se developpe chez les patients ages presentant plusieurs comorbidites. ...Elle presenteun aspect macroscopique et endoscopique caracteristique avec une decoloration noire diffuse et circonferentielle de la muqueuse œsophagienne. La plupart des patients presentent des saignements gastro-intestinaux. Parmi les autres symptômes, citons la dysphagie, les douleurs epigastriques ou ceux lies aux troubles sous-jacents. Letiologie a ete liee a plusieurs possibilites, telles quun reflux gastro-œsophagien, une hypoperfusion et une ischemie. Les facteurs de risque comprennent essentiellement lage avance, le sexe (masculin), les maladies cardiaques, lacidocetose diabetique, la malnutrition, les maladies renales et les traumatismes, qui ont egalement tendance a compliquer levolution de la maladie. Une biopsie de lœsophage nest pas justifiee. Son traitement comprend une hydratation suffisante, les inhibiteurs de la pompe a protons (IPP), du sucralfate, une nutrition parenterale. Lintervention chirurgicale est reservee aux patients presentant un tableau grave avec ulceration œsophagienne etendue, necrose et, dans certains cas, perforation œsophagienne. La prise en charge des comorbidites preexistantes associees est cruciale pour prevenir lexacerbation de levolution de la maladie qui pourrait se traduire par un mauvais pronostic et un taux de mortalite accru. Elle est associee a un taux de mortalite eleve necessitant un diagnostic rapide surtout chez certains patients a risque, en vue dune prise en charge precoce.
In this work, nine commonly used dosimetry detectors have been investigated to determine suitable relative dosimeters for kilovoltage x-ray beams. By comparison with the Monte Carlo calculated data, ...it was determined that for the detectors studied the PTW N23342, Markus and NACP parallel-plate chambers are more suitable for the measurement of percentage depth dose (PDD) data for this beam quality range with an uncertainty of about 3%. A diode detector may be used to measure the PDD for the 100 kVp beam, but it is not suitable for higher energies (300 kVp). The Capintec parallel-plate chamber may be adequate for medium-energy photons, but it has a slightly higher uncertainty for low-energy x-rays (100 kVp). For the measurement of beam profiles, diode and film yield incorrect profile tails, which can be corrected using the RK ionization chamber.
In this paper we present the dosimetric data of a Therapax DTX300 kilovoltage x-ray unit for endocavitary rectal irradiation. The unit if operated at tube voltage of 40–60 kVp (30 mA) with an added ...filtration of 0.2–0.4 mm Al generates acceptable beam qualities comparable to those of the original Papillon technique. Relative dosimetric measurements were performed at the cone end (37.2 cm SSD) of a 3 cm diameter rectal cone using various detectors to ensure the accuracy. A Monte Carlo method was used to calculate correction factors for the diode used in the percentage depth-dose (PDD) measurement, and to study the effect of the detector size on the beam profile. The PDD data were determined using the diode measurement corrected for its energy and angular response. It was found that the PTW N23342 and Markus parallel-plate chamber can be used directly to measure the PDD for this beam quality with 2% uncertainty. Measurement and Monte Carlo results have shown that the detector size has a significant effect on the penumbral profile. Film and diode detectors have a better spatial resolution compared to ionization chambers, but they may give an incorrect profile tail due to either nonlinear response at low energy or angular dependence. This can be corrected using the ionization-chamber measurement, based on the Monte Carlo analysis. The isodose distributions for this x-ray unit are presented.
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The effects of extended SSD (ESSD) on orthovoltage x-ray therapy dosimetry have been studied for a Therapax DXT300 treatment unit with several open- and close-ended cones. For the open-ended cones, ...the beam output and percentage depth dose (PDD) at ESSD can be accurately estimated from the measured data at the nominal SSD (NSSD) by an inverse square law (ISL) and a divergence factor for gaps (distance from cone end to point of interest) up to 15 cm. In the case of close-ended applicators (with an end plate of 3.2 mm thick PMMA), extending SSD results in significant changes in output and in PDDs, but has little effect on beam penumbra and flatness for gaps up to 15 cm. The output at ESSD calculated by applying the ISL with the NSSD is found to be as much as 9% different from the measurement for the close-ended cone. The output at ESSD can, however, be calculated accurately by applying the ISL with an effective SSD or using a measured gap factor. The change in the PDDs with SSD can be calculated from a geometric divergence using a pseudo SSD which is approximately equal to 60% of the effective SSD determined in air. The calculated PDD curves at ESSD using this divergence factor agree well with measurements (within +/- 1% for beams of 100-300 kVp with cone size ranging from 10 x 10 to 20 x 20 cm2 and gap distance up to 15 cm).
Cette thèse porte sur l'interopérabilité et la qualité de service dans les réseaux de 4ème génération. En particulier, nous proposons des solutions d'intégration entre le réseau WiMAX et le système ...satellite DVB-RCS en s'appuyant sur le standard IEEE 802.21. Trois solutions peuvent être mises en place pour l'interconnexion de réseaux sans fil. Il s'agit de la technologie GAN soutenue par le 3GPP, du protocole FMIP proposé par l'IETF et du standard IEEE 802.21. Notre choix se porte sur ce denier standard car il propose un cadre générique pour l'interopérabilité des réseaux. En fait, nous proposons une architecture satellitaire à base de WiMAX, DVB-RCS et IEEE 802.21 et nous décrivons aussi la procédure de handover WiMAX/DVB-RCS. Par ailleurs, nous améliorons les performances des réseaux WiMAX en utilisant un handover horizontal avec un mécanisme de réservation de ressources. Ensuite, le réseau WiMAX est intégré dans un système satellite DVB-RCS afin d'étudier les performances de cette convergence avec une réservation de ressources. Les résultats obtenus montrent que les mécanismes de réservation améliorent les performances. Afin de permettre au trafic de passer d'un réseau à l'autre en garantissant une qualité de service, une mise en correspondance de la qualité de service entre les réseaux WiMAX et DVB-RCS est proposée. En outre, nous proposons un mécanisme d'admission de connexion CAC dans le cadre de l'interconnexion WiMAX/DVB-RCS. Plusieurs stratégies sont prises en compte afin de permettre une coopérative efficace entre les deux systèmes.
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