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Nahla Abdellatif, Radhouane Fekih-Salem, Tewfik Sari
We study a model of the chemostat with several species in competition for a single resource. We take into account the intra-specific interactions between individuals of the same population of micro-organisms and we assume that the growth rates are increasing and the dilution rates are distinct. Using the concept of steady-state characteristics, we present a geometric characterization of the existence and stability of all equilibria. Moreover, we provide necessary and sufficient conditions on the control parameters of the system to have a positive equilibrium...
August 1, 2016: Mathematical Biosciences and Engineering: MBE
Antonis Nicolaides, Tewfik Soulimane, Constantinos Varotsis
Time-resolved step-scan FTIR spectroscopy has been employed to probe the dynamics of the ba₃ oxidoreductase from Thermus thermophilus in the ns-μs time range and in the pH/pD 6-9 range. The data revealed a pH/pD sensitivity of the D372 residue and of the ring-A propionate of heme a₃. Based on the observed transient changes a model in which the protonic connectivity of w941-w946-927 to the D372 and the ring-A propionate of heme a₃ is described.
2016: International Journal of Molecular Sciences
S Catanzaro, C Copelli, A Manfuso, K Tewfik, N Pederneschi, L Cassano, R Cocchi
PURPOSE: The surgical removal of head and neck tumors often represents a highly complex surgery. The three-dimensionality and the anatomy of the head and neck area make sometimes difficult a correct intraoperative orientation and the obtaining of an adequate oncological safety. In the present pilot study, the authors propose a protocol of application of intraoperative navigation in the resection of head and neck tumors. The purpose is to develop a methodology that can be helpful to ensure oncologic free margins of resection and to facilitate the orientation of the specimen by pathologists...
September 22, 2016: International Journal of Computer Assisted Radiology and Surgery
Joey L Meadows, Tewfik J Bichay
No abstract text is available yet for this article.
September 2016: Medical Physics
Tewfik J Bichay, Alan Mayville
Stereotactic radiosurgery (SRS) treatment is characterized by high doses per fraction and extremely steep dose gradients. This requires a great degree of accurate localization to the appropriate treatment position, and continuous immobilization during the treatment session. In the case of Trigeminal Neuralgia (TGN) treatment this is especially true as the very small target volume makes positional accuracy critical. In this study we carried out a quantitative analysis of patient motion during the full treatment fraction within a radiosurgery immobilization mask system...
2016: Curēus
Nagwa Meguid, Mona Anwar, Safaa Zaki, Wafaa Kandeel, Nihad Ahmed, Ihab Tewfik
AIM: In the hope to assist in tailoring individualized nutritional therapy, this study aimed to assess the nutritional status of autistic children. MATERIAL AND METHODS: This cross-sectional study included 80 autistic children, divided into two groups: group 1 (aged 3- 5 years) and group 2 (aged 6-9 years). Diagnosis was performed based on the criteria for autistic disorder as defined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Autism Diagnostic Interview Revised and Autism Rating Scale...
June 15, 2015: Open Access Macedonian Journal of Medical Sciences
Neha Kapoor, Jane Naufahu, Sundus Tewfik, Sushma Bhatnagar, Rakesh Garg, Ihab Tewfik
Purpose Advanced cancer patients with disease progression develop cachexia. Nevertheless, cancer patients at nutritional risk have shown improved body weight and quality of life with oral nutritional supplements. Method This was a randomized controlled trial in adult female cancer patients (n = 63) attending palliative clinics, with symptoms of cachexia. Eligible patients were randomly distributed into control (n = 33) and intervention (n = 30) groups. Both groups were provided with nutritional and physical activity counseling, but the intervention group received an additional 100 g of Improved Atta (IAtta) for 6 months daily consumption...
June 1, 2016: Integrative Cancer Therapies
Ronen Sosnik, Vijay Aditya Tadipatri, Ahmed H Tewfik, Giuseppe Pellizzer
To date, decoding accuracy of actual or imagined pointing movements to targets in 3D space from electroencephalographic (EEG) signals has remained modest. The reason may pertain to the fact that these movements activate essentially the same neural networks. In this study, we aimed at testing whether repetitive pointing movements to each of the targets promotes the development of segregated neural patterns, resulting in enhanced decoding accuracy. Six human subjects generated slow or fast repetitive pointing movements with their right dominant arm to one of five targets distributed in 3D space, followed by repetitive imagery of movements to the same target or to a different target...
August 4, 2016: Neuroscience
Antonis Nicolaides, Tewfik Soulimane, Constantinos Varotsis
Nanosecond time-resolved step-scan FTIR spectroscopy (nTRS (2) -FTIR) has been applied to literally probe the active site of the carbon monoxide (CO)-bound thermophilic ba3 heme-copper oxidoreductase as it executes its function. The nTRS (2) - snapshots of the photolysed heme a3 Fe-CO/CuB species captured a "transition state" whose side chains prevent the photolysed CO to enter the docking cavity. There are three sets of ba3 photoproduct bands of docked CO with different orientation exhibiting different kinetics...
September 2016: Biochimica et Biophysica Acta
Marco A Mascarella, Marc A Tewfik, Majed Aldosari, Denis Sirhan, Anthony Zeitouni, Salvatore Di Maio
OBJECTIVE: To identify clinico-radiologic factors associated with incomplete anterior cranial fossa (ACF) meningioma resection via an endoscopic endonasal approach. METHOD: Patients undergoing endoscopic endonasal resection of an ACF meningioma were retrospectively accrued from two university-affiliated centers. Demographic profiles and radiologic findings, including tumor dimensions and morphology, anatomic location, and vascular involvement, were stratified according to the extent of resection...
July 2016: World Neurosurgery
Vijay Aditya Tadipatri, Ahmed Tewfik, Guiseppe Pellizzer, James Ashe
Long-term variability remains one of the major hurdles in using intra-cortical recordings like local field potentials for brain computer interfaces (BCI). Practical neural decoders need to overcome time instability of neural signals to estimate subject behavior accurately and faithfully over the long-term. This paper presents a novel decoder that a) characterizes each behavioral task (i.e. different movement directions under different force conditions) with multiple neural patterns and; b) adapts to the long-term variations in neural features by identifying the stable neural patterns...
April 20, 2016: IEEE Transactions on Bio-medical Engineering
Tewfik Sari, Jérôme Harmand
Many microbial ecosystems can be seen as microbial 'food chains' where the different reaction steps can be seen as such: the waste products of the organisms at a given reaction step are consumed by organisms at the next reaction step. In the present paper we study a model of a two-step biological reaction with feedback inhibition, which was recently presented as a reduced and simplified version of the anaerobic digestion model ADM1 of the International Water Association (IWA). It is known that in the absence of maintenance (or decay) the microbial 'food chain' is stable...
May 2016: Mathematical Biosciences
Joe Saliba, Naif Fnais, Marcel Tomaszewski, Junie S Carriere, Saul Frenkiel, Johannes Frasnelli, Marc A Tewfik
OBJECTIVES/HYPOTHESIS: Trigeminal sensation (TS) within the nasal cavity is important for the perception of nasal airflow. The objective of this study is to examine whether impaired TS contributes to the sensation of nasal obstruction in patients with chronic rhinosinusitis (CRS). STUDY DESIGN: Prospective case-control study conducted in a tertiary referral rhinology clinic. METHODS: Cases consisted of CRS patients with subjective nasal obstruction, not previously treated with oral corticoids...
May 2016: Laryngoscope
Peter-John Wormald, Yi Chen Zhao, Constanza J Valdes, Alvaro E Pacheco, Thanh Ngoc Ha, Marc A Tewfik, David Wabnitz, Chi-Kee Leslie Shaw
BACKGROUND: There are many standard repair options for choanal atresia including puncture, dilatation and drilling of the atretic plate. Most of these techniques involve postoperative stenting, which may promote granulation and scarring, with possible progression to restenosis. This article describes a novel approach for choanal atresia repair without postoperative stenting. METHODS: This article describes our experience with this choanal atresia repair technique utilized in 16 pediatric patients and 1 adult patient across multiple tertiary pediatric and rhinology centers during 2008 through 2015...
June 2016: International Forum of Allergy & Rhinology
Alexander Tewfik, Susan S Bell, Kevin S McCann, Kristina Morrow
Empirical patterns that emerge from an examination of food webs over gradients of environmental variation can help to predict the implications of anthropogenic disturbance on ecosystems. This "dynamic food web approach" is rarely applied at the coastal margin where aquatic and terrestrial systems are coupled and human development activities are often concentrated. We propose a simple model of ghost crab (Ocypode quadrata) feeding that predicts changing dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) along a gradient of beach morphology and test this model using a suite of 16 beaches along the Florida, USA coast...
2016: PloS One
Mohammed Mesk, Tewfik Mahdjoub, Sébastien Gourbière, Jorge E Rabinovich, Frédéric Menu
Demographic processes and spatial dispersal of Triatoma dimidiata, a triatomine species vector of Chagas disease, are modeled by integrodifference equations to estimate invasion capacity of this species under different ecological conditions. The application of the theory of orthogonal polynomials and the steepest descent method applied to these equations, allow a good approximation of the abundance of the adult female population and the invasion speed. We show that: (1) under the same mean conditions of demography and dispersal, periodic spatial dispersal results in an invasion speed 2...
April 21, 2016: Journal of Theoretical Biology
C Copelli, A Manfuso, A d'Ecclesia, S Catanzaro, L Cassano, N Pederneschi, K Tewfik Hanna, R Cocchi
The aim of this study is to describe the reduction of medial orbital wall fractures using a combination of two different techniques: the endoscopic reduction and the navigation aided reconstruction. The endoscopic approach avoids an external incision and allows the observation of the fracture site clearly. Navigation-aided reconstruction is essential to achieve precise and predictable results in orbital reconstruction. It consists in an ideal virtual reconstruction of the target area created using a mirroring tool, and superimposing and comparing the unaffected and the affected sides...
December 2015: Journal of Cranio-maxillo-facial Surgery
Roger Arditi, Claude Lobry, Tewfik Sari
The standard model for the dynamics of a fragmented density-dependent population is built from several local logistic models coupled by migrations. First introduced in the 1970s and used in innumerable articles, this standard model applied to a two-patch situation has never been completely analysed. Here, we complete this analysis and we delineate the conditions under which fragmentation associated to dispersal is either beneficial or detrimental to total population abundance. Therefore, this is a contribution to the SLOSS question...
December 2015: Theoretical Population Biology
Darrion L Mitchell, Chad R Tracy, John M Buatti, Mark C Smith, Anthony N Snow, Michael D Henry, Daniel A Vaena, Hamed H Tewfik, John M Watkins
Radiation therapy indications in the postprostatectomy setting are evolving. Several retrospective series have identified a number of "high-risk" pathologic features associated with an elevated risk of disease recurrence after radical prostatectomy. More recently, several randomized phase III trials demonstrated superior biochemical relapse-free survival for adjuvant radiation therapy after prostatectomy for patients with these high-risk pathologic features, including positive margin status, extraprostatic extension, and/or seminal vesicle invasion...
February 2016: Clinical Genitourinary Cancer
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