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Search Results: 1 - 10 of 682 matches for " Amina Taleb Ibrahimi "
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Dirac cone with helical spin polarization in ultrathin $α$-Sn(001) films
Yoshiyuki Ohtsubo,Patrick Le Fèvre,Fran?ois Bertran,Amina Taleb-Ibrahimi
Physics , 2013, DOI: 10.1103/PhysRevLett.111.216401
Abstract: Spin-split two-dimensional electronic states have been observed on ultrathin Sn(001) films grown on InSb(001) substrates. Angle-resolved photoelectron spectroscopy (ARPES) performed on these films revealed Dirac-cone-like linear dispersion around the $\bar{\Gamma}$ point of surface Brillouin zone, suggesting nearly massless electrons belonging to 2D surface states. The states disperse across a bandgap between bulk-like quantum well states in the films. Moreover, both circular dichroism of ARPES and spin-resolved ARPES studies show helical spin polarization of the Dirac-cone-like surface states, suggesting a topologically protected character as in a bulk topological insulator (TI). These results indicate that a quasi-3D TI phase can be realized in ultrathin films of zero-gap semiconductors.
Non-trivial Surface-band Dispersion on Bi(111)
Yoshiyuki Ohtsubo,Luca Perfetti,Mark Oliver Goerbig,Patrick Le Fèvre,Fran?ois Bertran,Amina Taleb-Ibrahimi
Physics , 2013, DOI: 10.1088/1367-2630/15/3/033041
Abstract: We performed angle-resolved photoelectron spectroscopy of the Bi(111) surface to demonstrate that this surface support edge states of non-trivial topology. Along the $\bar{\Gamma}\bar{M}$-direction of the surface Brillouin zone, a surface-state band disperses from the projected bulk valence bands at $\bar{\Gamma}$ to the conduction bands at $\bar{M}$ continuously, indicating the non-trivial topological order of three-dimensional Bi bands. We ascribe this finding to the absence of band inversion at the $L$ point of the bulk Bi Brillouin zone. According to our analysis, a modification of tight-binding parameters can account for the non-trivial band structure of Bi without any other significant change on other physical properties.
Wide-Gap Semiconducting Graphene from Nitrogen-Seeded SiC
Feng Wang,Gang Liu,Sara Rothwell,Meredith Nevius,Antonio Tejeda,Amina Taleb-Ibrahimi,Leonard Feldman,Philip Cohen,Edward Conrad
Physics , 2013, DOI: 10.1021/nl402544n
Abstract: All carbon electronics based on graphene has been an elusive goal. For more than a decade, the inability to produce significant band-gaps in this material has prevented the development of semiconducting graphene. While chemical functionalization was thought to be a route to semiconducting graphene, disorder in the chemical adsorbates, leading to low mobilities, have proved to be a hurdle in its production. We demonstrate a new approach to produce semiconducting graphene that uses a small concentration of covalently bonded surface nitrogen, not as a means to functionalize graphene, but instead as a way to constrain and bend graphene. We demonstrate that a submonolayer concentration of nitrogen on SiC is sufficient to pin epitaxial graphene to the SiC interface as it grows, causing the graphene to buckle. The resulting 3-dimensional modulation of the graphene opens a band-gap greater than 0.7eV in the otherwise continuous metallic graphene sheet.
Exceptional ballistic transport in epitaxial graphene nanoribbons
Jens Baringhaus,Ming Ruan,Frederik Edler,Antonio Tejeda,Muriel Sicot,Amina Taleb Ibrahimi,Zhigang Jiang,Edward Conrad,Claire Berger,Christoph Tegenkamp,Walt A. de Heer
Physics , 2013, DOI: 10.1038/nature12952
Abstract: Graphene electronics has motivated much of graphene science for the past decade. A primary goal was to develop high mobility semiconducting graphene with a band gap that is large enough for high performance applications. Graphene ribbons were thought to be semiconductors with these properties, however efforts to produce ribbons with useful bandgaps and high mobility has had limited success. We show here that high quality epitaxial graphene nanoribbons 40 nm in width, with annealed edges, grown on sidewall SiC are not semiconductors, but single channel room temperature ballistic conductors for lengths up to at least 16 micrometers. Mobilities exceeding one million corresponding to a sheet resistance below 1 Ohm have been observed, thereby surpassing two dimensional graphene by 3 orders of magnitude and theoretical predictions for perfect graphene by more than a factor of 10. The graphene ribbons behave as electronic waveguides or quantum dots. We show that transport in these ribbons is dominated by two components of the ground state transverse waveguide mode, one that is ballistic and temperature independent, and a second thermally activated component that appears to be ballistic at room temperature and insulating at cryogenic temperatures. At room temperature the resistance of both components abruptly increases with increasing length, one at a length of 160 nm and the other at 16 micrometers. These properties appear to be related to the lowest energy quantum states in the charge neutral ribbons. Since epitaxial graphene nanoribbons are readily produced by the thousands, their room temperature ballistic transport properties can be used in advanced nanoelectronics as well.
Topological surface states of strained Mercury-Telluride probed by ARPES
Olivier Crauste,Yoshiyuki Ohtsubo,Philippe Ballet,Pierre André Louis Delplace,David Carpentier,Clément Bouvier,Tristan Meunier,Amina Taleb-Ibrahimi,Laurent Lévy
Physics , 2013,
Abstract: The topological surface states of strained HgTe have been measured using high-resolution ARPES measurements. The dispersion of surface states form a Dirac cone, which origin is close to the top of the \ghh band: the top half of the Dirac cone is inside the stress-gap while the bottom half lies within the heavy hole bands and keeps a linear dispersion all the way to the X-point. The circular dichroism of the photo-emitted electron intensity has also been measured for all the bands.
Surface Tomonaga-Luttinger liquid state on Bi/InSb(001)
Yoshiyuki Ohtsubo,Jun-ichiro Kishi,Kenta Hagiwara,Patrick Le Fèvre,Fran?ois Bertran,Amina Taleb-Ibrahimi,Masaharu Matsunami,Hiroyuki Yamane,Shin-ichiro Ideta,Kiyohisa Tanaka,Shin-ichi Kimura
Physics , 2015, DOI: 10.1103/PhysRevLett.115.256404
Abstract: A 1D metallic surface state was created on an anisotropic InSb(001) surface covered with Bi. Angle-resolved photoelectron spectroscopy (ARPES) showed a 1D Fermi contour with almost no 2D distortion. Close to the Fermi level ($E_{\rm F}$), the angle-integrated photoelectron spectra showed power-law scaling with the binding energy and temperature. The ARPES plot above $E_{\rm F}$ obtained thanks to thermally broadened Fermi edge at room temperature showed a 1D state with continuous metallic dispersion across $E_{\rm F}$ and power-law intensity suppression around $E_{\rm F}$. These results strongly suggest a Tomonaga-Luttinger liquid on the Bi/InSb(001) surface.
Symmetry of the Fermi surface and evolution of the electronic structure across the paramagnetic-helimagnetic transition in MnSi/Si(111)
Alessandro Nicolaou,Matteo Gatti,Elena Magnano,Patrick Le Fèvre,Federica Bondino,Fran?ois Bertran,Antonio Tejeda,Michèle Sauvage-Simkin,Alina Vlad,Yves Garreau,Alessandro Coati,Nicolas Guérin,Fulvio Parmigiani,Amina Taleb-Ibrahimi
Physics , 2015, DOI: 10.1103/PhysRevB.92.081110
Abstract: MnSi has been extensively studied for five decades, nonetheless detailed information on the Fermi surface (FS) symmetry is still lacking. This missed information prevented from a comprehensive understanding the nature of the magnetic interaction in this material. Here, by performing angle-resolved photoemission spectroscopy on high-quality MnSi films epitaxially grown on Si(111), we unveil the FS symmetry and the evolution of the electronic structure across the paramagnetic-helimagnetic transition at T$_C$ $\sim$ 40 K, along with the appearance of sharp quasiparticle emission below T$_C$. The shape of the resulting FS is found to fulfill robust nesting effects. These effects can be at the origin of strong magnetic fluctuations not accounted for by state-of-art quasiparticle self-consistent GW approximation. From this perspective, the unforeseen quasiparticle damping detected in the paramagnetic phase and relaxing only below T$_C$, along with the persistence of the d-bands splitting well above T$_C$, at odds with a simple Stoner model for itinerant magnetism, open the search for exotic magnetic interactions favored by FS nesting and affecting the quasiparticles lifetime.
Association between Overexpression of Her-2 and Other Clinicopathologic Prognostic Factors in Breast Cancer in Morocco  [PDF]
Zineb Bouchbika, Nadia Benchakroun, Amina Taleb, Hassan Jouhadi, Nezha Tawfiq, Souha Sahraoui, Abdellatif Benider
Journal of Cancer Therapy (JCT) , 2012, DOI: 10.4236/jct.2012.325099
Abstract: Background: Breast cancer is the leading cancer among women. The management depends largely on the knowledge of prognostic factors. The aim of our study is to evaluate the overexpression of Her-2/neu in patients with invasive breast carcinoma in Morocco, and to study the association between this overexpression and otherprognostic factors of breast cancer, such as age, tumor size, tumor grade, hormone receptors, vascular space invasion and lymph node status. Methods: This is a transversal study in which we included patients with invasive breast carcinomas treated at University Hospital Ibn Rochd of Casablanca in radiotherapy-oncology departement between January 2008 and December 2010, having had surgery first. Univariate analysis (Chi 2 test and Student’s test) and multivariate (logistic regression) were performed to study this association. Results: The overexpression of Her-2/neu was found in 29.2% of cases. In univariate analysis, Her-2 positive status was significantly correlated with high-grade tumors and large, to a lymph node, vascular space invasion and negative ER/PR. Age alone does not appear as a factor associated with positive Her-2/neu status. In multivariate analysis, the overexpression of Her 2 was significantly associated only with vascular space invasion, high tumor grade and the negativity of estrogen receptors. Conclusion: In our series, only the high grade, the vascular space invasion and the negative hormone receptors are independent factors associated with overexpression of Her 2/neu. Age does not appear as a factor associated with positive Her-2/neu status.
Surgical Bypass versus Endoscopic Stenting for Unresectable Head Pancreatic Cancer, Which Palliative Treatment Is Better in Developing Countries, Morocco as an Example  [PDF]
Khalid Mazine, Hamdaoui Mohammed, El Ghazi Karima, Ousadden Abdelmalek, Mazaz Khalid, Ibrahimi Adil, Ait Taleb Khalid, Benajeh Dafrallah, Benjelloun Elbachir
Open Journal of Gastroenterology (OJGas) , 2017, DOI: 10.4236/ojgas.2017.75017
Abstract: Background: Metal stents for unresectable pancreatic cancer are associated with longer patency and superior cost-effectiveness. However, they are too expensive to be recommended routinely in developing countries. Moreover, a debate on outcome results in these patients who receive plastic biliary endoprothesis versus surgical bypass as palliation of obstructive jaundice. We aimed to compare retrospectively the outcomes in patients treated with plastic stent or surgical bypass as a palliative option for these patients. Patients and Methods: We have examined data for patients (n = 86) who received endoscopic stenting (n = 64) or surgical bypass (n = 22), from January 2013 to November 2016, as a palliative treatment for obstructive jaundice from inoperable cancer head pancreas. Results: Serum bilirubin and CA19.9 levels were comparable in age and gender matched patient groups. Moreover, post-operative major complications and 30-days mortality showed no significant differences among patient groups. However, surgical bypass treated patients showed longer initial hospital stay (9 vs. 6 days, p = 0.014), higher cost ($1600 vs. $1088) and longer survival (192 vs. 101 days, p = 0.003) compared to endoscopy-stenting treated patients. Re-hospitalization was required for 5 stented patients (averaged $448). Conclusion: Biliary bypass surgery for unresectable pancreatic cancer may improve patient survival, although prolongs hospital stay. It may be recommended for relatively fit patients with a life expectancy of 6 months and more.
Superior Mesenteric Arterial Embolism Associated with an Acute Limb Ischemia: A Case Report and Literature Review  [PDF]
Abdesslam Bouassria, Elbachir Benjelloun, Imane Kamaoui, Hicham Elbouhaddouti, Ouadii Mouaqit, Abdelmalek Ousadden, Khalid Mazaz, Khalid Ait Taleb, Laila Sedreddine, Mohammed El Abkari, SidiAdil Ibrahimi, Ihssane Mellouki
Open Journal of Gastroenterology (OJGas) , 2014, DOI: 10.4236/ojgas.2014.44027
Abstract: Introduction: Acute mesenteric ischemia due to an embolism of the superior mesenteric artery (SMA) is associated with a high mortality rate. Over twenty per cent of acute mesenteric embolism cases consist of multiple emboli. Case Presentation: We present a rare case of a 62-year-old man admitted with acute abdominal pain and signs of intestinal occlusion related to an acute mesenteric ischemia due to superior mesenteric arterial embolism. It was associated with a synchronous acute bilateral lower limb ischemia due to embolic arterial occlusion. He underwent an emergency explorative laparotomy with proximal jejunal resection, and the patient made an excellent recovery. As for the acute limb ischemia, it was treated by efficient anticoagulation allowing limb salvage. Conclusion: When treating a superior mesenteric arterial embolism, the possibility of recurrent or multiple arterial thromboembolic events should be considered. A prompt diagnosis, aggressive surgical treatment and intensive care could improve the prognosis.
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