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- Pierre S Youssef
- 2013

We extend to the matrix setting a recent result of Srivastava-Vershynin [21] about estimating the covariance matrix of a random vector. The result can be interpreted as a quantified version of the law of large numbers for positive semi-definite matrices which verify some regularity assumption. Beside giving examples, we discuss the notion of log-concaveâ€¦ (More)

- Pierre S Youssef
- 2013

We prove a normalized version of the restricted invertibility principle obtained by Spielman-Srivastava in [15]. Applying this result, we get a new proof of the proportional Dvoretzky-Rogers factorization theorem recovering the best current estimate in the symmetric setting while we improve the best known result in the nonsymmetric case. As a consequence,â€¦ (More)

- Alexander E. Litvak, Anna Lytova, Konstantin E. Tikhomirov, Nicole Tomczak-Jaegermann, Pierre S Youssef
- 2016

Let Dn,d be the set of all d-regular directed graphs on n vertices. Let G be a graph chosen uniformly at random from Dn,d and M be its adjacency matrix. We show that M is invertible with probability at least 1 âˆ’ C ln d/ âˆš d for C â‰¤ d â‰¤ cn/ ln n, where c, C are positive absolute constants. To this end, we establish a few properties of d-regular directedâ€¦ (More)

- Alexander E. Litvak, Anna LYTOVA, Konstantin E. Tikhomirov, Nicole Tomczak-Jaegermann, Pierre S Youssef
- 2015

Let Dn,d be the set of all directed d-regular graphs on n vertices. Let G be a graph chosen uniformly at random from Dn,d and M be its adjacency matrix. We show that M is invertible with probability at least 1âˆ’C ln d/ âˆš d for C â‰¤ d â‰¤ cn/ ln n, where c, C are positive absolute constants. To this end, we establish a few properties of directed d-regularâ€¦ (More)

- Pierre S Youssef
- 2013

Given a matrix U , using a deterministic method, we extract a "large" submatrix of Å¨ (whose columns are obtained by normalizing those of U ) and estimate its smallest and largest singular value. We apply this result to the study of contact points of the unit ball with its maximal volume ellipsoid. We consider also the paving problem and give a deterministicâ€¦ (More)

- Vanda G Yazbek-Karam, Roula W Haswani, +8 authors Marie T. Aouad
- Journal of clinical anesthesia
- 2009

A reusable Robertshaw red rubber double-lumen endotracheal tube (DLT) was placed to facilitate lung isolation for thoracoscopy in a 49-year-old atopic patient. In spite of its smooth insertion, it was then not possible to remove the DLT. Direct laryngoscopy showed severe laryngeal edema. After 48 hours of medical treatment with steroids, the trachea wasâ€¦ (More)

- Ingo K Schumacher, Andreas Hunsicker, Pierre S Youssef, Dietmar Lorenz
- Saudi medical journal
- 2002

OBJECTIVE
Current problems in gastric cancer surgery concern the extent of gastric resection, the need for abdominal evisceration, the degree of lymphadenectomy, and an optimal preoperative tumor staging procedure.
METHODS
A retrospective clinical trial of 284 patients who underwent surgery at Ernst-Moritz-Arndt-University, Greifswald, Germany for gastricâ€¦ (More)

- Alexander E. Litvak, Anna Lytova, Konstantin E. Tikhomirov, Nicole Tomczak-Jaegermann, Pierre S Youssef
- 2017

We derive a lower bound on the smallest singular value of a random d-regular matrix, that is, the adjacency matrix of a random d-regular directed graph. More precisely, let C1 < d < c1n/ log 2 n and let Mn,d be the set of all 0/1-valued square n Ã— n matrices such that each row and each column of a matrix M âˆˆ Mn,d has exactly d ones. Let M be uniformlyâ€¦ (More)

- Pierre S Youssef, L H Wihelm, GÃ¼nther Schwesinger, Thomas D. Howell, Joerg Petermann, Richard Zippel
- Saudi medical journal
- 1999

Full text is available as a scanned copy of the original print version.

- Tony El Murr, Pierre S Youssef, Saad Khairallah, Fady Sleilaty, Elie Ghayad
- Le Journal medical libanais. The Lebanese medicalâ€¦
- 2006

Benign cystic lymphangioma is a relatively rare tumor of the human body. It's more frequent in young patients. It is usually localized in the neck but may have mediastinal or intra-abdominal localization. It's usually asymptomatic with good prognosis after total excision. We report in this article the case of a young man with a huge mediastinal cysticâ€¦ (More)