Nonresonant Raman spectrum of C60 nanopeapod: C60 polymerization effects

We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one.We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one

Raman-Active modes in Homogeneous and Inhomogeneous Bundle of Single-Walled Carbon Nanotubes

In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied.In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied

Size And Chirality Effects On Raman Spectrum Of Double-Wall Carbon Nanotube Bundle

We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size.We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size

Modelling and simulation of vibrationnal properties of carbon nanotubes and derivatives

The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods.The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods

Raman active modes in single-walled boron nitride nanotube bundles

We use the spectral moments method in the framework of the bond-polarization theory to calculate polarized nonresonant Raman spectra of chiral and achiral bundles of single walled boron nitride nanotubes (BWBNNTs) as a function of their diameter and chirality. The Spectra are computed for infinite size of BWBNNTs. We used a Lennard-Jones potential to describe the van der waals intertube interactions between tubes in a bundle. We show that the Raman active modes in the low wave number region are very sensitive to the nanotube diameter. We found that for infinite nanotube bundles, additional Radial Breathing Like mode appears in the low wave number region. These results are useful to interpret the experimental Raman spectra of BWBNNTs

Finite size effects on Raman spectrum of single-walled boron nitride nanotube

Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs.Using the spectral moments method, we present calculations of Raman active modes of Single Walled Boron Nitride Nanotube (SW-BNNT). The Spectra are computed for chiral and achiral nanotubes in terms of their diameter and length. The behaviors of low frequency Raman active modes characteristic, in terms of the tube diameter revealed that these frequencies are diameter dependent. We show that the number of Raman active modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. These predictions are useful to interpret the experimental Raman spectra of BNNTs

Volvulus du grêle sur mésentère commun incomplet une redoutable complication rare chez l’adulte: à propos de 1 cas

Le mésentère commun résulte d'une anomalie de rotation du tube digestif. Il est caractérisé par la persistance d'une disposition anatomique embryonnaire secondaire à une anomalie de rotation de l'anse ombilicale primitive, constituant ainsi un méso commun à toute l'anse intestinale etune racine du mésentère extrêmement courte. Cette insuffisance de rotation est le plus souvent associée à un défaut d'accolement. Ces  anomalies de rotation intestinale peuvent aboutir à des complications redoutables parfois mortelles, qui surviennent généralement au cours de la période néonatale où à l'âge pédiatrique. On estime que la prévalence de ces malformations congénitales à l'âge adulte est de l'ordre de 0,2% à 0,5% âge auquel elles demeurent très souvent asymptomatiques et donc non diagnostiquées. Le diagnostic de volvulus total du grêle peut se faire dans des circonstances très variées: en urgence devant un tableau  d'occlusion intestinale aiguë, voire un état de choc pouvant conduire au décès, devant un tableau de douleurs abdominales répétées plus ou moins associées à des troubles du transit. Nous rapportons l'observation d'un patient de 18 ans admis pour volvulus total du grêle sur mésentère commun incomplet chez qui l'évolution était favorable

Risque d'érosion hydrique entre fragilité des équilibres environnementaux et perspectives de durabilité: Cas du bassin d’Oued El Abed (Maroc nord-est)

The objective of this work is to study water erosion phenomenon in El Abed watershed in North Eastern Morocco. With this in mind, we have analyzed the quantitative and qualitative information available on the one hand, and on the other hand, we have carried out field measurements by rain simulation (60 mm/h during 10 mn). Soil loss was estimated using the universal soil loss equation (USLE). The qualitative analysis based on the inventory of the various forms of water erosion showed a strong morphodynamic activity, characterized by diffuse and concentrated streaming, gullying and side extensions of valleys. The quantitative analysis of soil losses using USLE model made it possible to estimate that 4,7% of the watershed surface area are strongly eroded and that average specific degradation is estimated to be 6,4 t/ha/an. Measurements of rain simulation tests showed clear differences between the various land uses. Indeed, runoff coefficient is low on the vegetation covered plots of and the plots cultivated parallel to contour lines. On the other hand, runoff coefficient is high on steeply bare soils. The amount of detached soil varied from 0.014 t/ha for the covered plots to 2.9 t/ha for the steeply bare soils. It should be underlined that the extent of water erosion in El Abed watershed is due to its natural settings, but also to anthropic activities (cultivation and overgrazing).  Keywords: Water erosion, USLE, El Abed watershed, MoroccoL'érosion hydrique est l’un des risques inquiétants qui menacent le milieu physique et la stabilité humaine. Le bassin d’oued El Abed, est sujet à ce phénomène depuis longtemps, ce qui a induit des mutations importantes et a touché divers domaines économiques, sociaux et environnementaux. Ainsi, la problématique de cette étude est axée sur l’étude de l’érosion et son évaluation dans ce bassin. Le bassin d’oued El Abed est situé au sud-ouest de Taourirt, dans la partie ouest du couloir de Guercif-Oujda et comprend une partie de la plaine de Tafrata. Sa surface est de 317 km² à sa confluence avec oued Moulouya. Pour étudier l'érosion dans ce bassin, nous avons, d’une part analysé les données quantitatives et qualitatives disponibles et, d’autre part, réalisé des mesures sur le terrain par simulation de pluie (intensité de 60 mm/h durant 10 mn). L'estimation de la perte en sol a été faite en se basant sur l'équation universelle de perte en sol (USLE). L'inventaire des diverses manifestations et formes d'érosion hydrique dans le bassin de l'oued El-Abed montre clairement qu'il s'agit d'une forte activité morphodynamique caractérisée par un ruissellement diffus et concentré, des ravinements, des extensions latérales des vallées. Après avoir calculé les différents facteurs de l’USLE, on a constaté que 4,7% de la surface du bassin serait fortement érodée. La dégradation spécifique moyenne a été estimée à 6,4 tonnes/ha/an. Les mesures de simulation de pluie ont montré des différences nettes entre les utilisations des terres. En effet, les coefficients de ruissellement sont faibles dans les parcelles couvertes de végétation et celles cultivées parallèlement aux courbes de niveau. Par contre, sur les sols nus et les pentes fortes, ce coefficient est élevé. Les quantités de sols détachées varient de 0,014 pour les parcelles couvertes à 2,9 t/ha pour celles nues et à forte pente. L’érosion dans le bassin d’El Abed est due à sa fragilité naturelle mais surtout aux actions anthropiques (mise en culture, surpâturage). Mots clés: Érosion hydrique, USLE, Bassin d’oued El-Abed, Maroc nord-es