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Papers by Abdulrhman Alsayed

Journal of Obesity, 2013

Background. Weight loss and reduction in comorbidities can be achieved by longitudinal sleeve gas... more Background. Weight loss and reduction in comorbidities can be achieved by longitudinal sleeve gastrectomy (LSG). Existing evidence suggests that LSG resolves or improves hyperlipidemia in morbidly obese patients. The aim of this study was to systematically review the effect of LSG on hyperlipidemia. Methods. A systematic literature search was conducted from Englishlanguage studies published from 2000 to 2012 for the following databases: MEDLINE, EMBASE, CINAHL, PubMed, Clinical evidence, Scopus, Dara, Web of Sciences, TRIP, Health Technology Database, Cochrane library, and PsycINFO. Results. A total of 4,211 articles were identified in the initial search, and 4,185 articles were excluded based on the exclusion criteria. Twenty-six studies met the inclusion criteria for this systematic review, involving 3,591 patients. The mean preoperative body mass index (BMI) was 48 ± 7.0 kg/m 2 (range 37.2-65.3). The mean postoperative BMI was 35 ± 5.9 kg/m 2 (range 26.3-49). The mean percentage of excess weight loss (EWL) was 63.1% (range 37.7-84.5), with a mean followup of 19.1 months (range 6-60). The mean levels of pre and post operative cholesterol were 194.4 ± 12.3 mg/dL (range 178-213) and 181 ± 16.3 mg/dL (range 158-200), respectively. Conclusion. Most patients with hyperlipidemia showed improvement or resolution of lipid profiles after LSG. Based on this systematic review, LSG has a significant effect on hyperlipidemia in the form of resolution or improvement in the majority of patients.

European Journal of Heart Failure Supplements, 2008

Physical Review Letters, 2004

We prepare a novel suspension composed of rodlike fd virus and thermosensitive polymer poly(N-iso... more We prepare a novel suspension composed of rodlike fd virus and thermosensitive polymer poly(N-isopropylacrylamide) whose phase diagram is temperature and concentration dependent. The system exhibits a rich variety of stable and metastable phases, and provides a unique opportunity to directly observe melting of lamellar phases and single lamellae. Typically, lamellar phases swell with increasing temperature before melting into the nematic phase. The highly swollen lamellae can be superheated as a result of topological nucleation barriers that slow the formation of the nematic phase.

Physical Review Letters, 2004

We report the creation of nematic nanotube gels containing large domains of isolated, oriented, h... more We report the creation of nematic nanotube gels containing large domains of isolated, oriented, half-micron-long, single-wall carbon nanotubes (SWNTs). We make them by homogeneously dispersing surfactant coated SWNTs at low concentration in an N-isopropyl acrylamide gel and then inducing a volume-compression transition. These gels exhibit hallmark properties of a nematic: birefrigence, anisotropy in optical absorption, and disclination defects. We also investigate the isotropic-to-nematic transition of these gels, and we describe the physical properties of their ensuing nematic state, including a novel buckling of sample walls. Finally, we provide a simple model to explain our observations.

Physical Review Letters, 2010

We study melting mechanisms in single and polycrystalline colloidal films composed of diametertun... more We study melting mechanisms in single and polycrystalline colloidal films composed of diametertunable microgel spheres with short-ranged repulsive interactions and confined between two glass walls. Thick films (>4 layers), thin-films ( 4 layers), and monolayers exhibit different melting behaviors. Thick films melt from grain boundaries in polycrystalline solid films and from film-wall interfaces in singlecrystal films; a liquid-solid coexistence regime is observed in thick films but vanishes at a critical thickness of 4 layers. Thin solid films (2 to 4 layers) melt into the liquid phase in one step from both grain boundaries and from within crystalline domains. Monolayers melt in two steps with a middle hexatic phase.

Physical Review E, 2008

Melting of two-dimensional colloidal crystals is studied by video microscopy. The samples were co... more Melting of two-dimensional colloidal crystals is studied by video microscopy. The samples were composed of microgel spheres whose diameters could be temperature tuned, and whose pair potentials were measured to be short ranged and repulsive. We observed two-step melting from the crystal to a hexatic phase and from the hexatic to the liquid phase as a function of the temperature-tunable volume fraction. The translational and orientational susceptibilities enabled us to definitively determine the phase transition points, avoiding ambiguities inherent in other analyses and resolving a "dislocation precursor stage" in the solid phase that some of the traditional analyses may incorrectly associate with the hexatic phase. A prefreezing stage of the liquid with ordered patches was also found.

Journal of Obesity, 2013

Background. Weight loss and reduction in comorbidities can be achieved by longitudinal sleeve gas... more Background. Weight loss and reduction in comorbidities can be achieved by longitudinal sleeve gastrectomy (LSG). Existing evidence suggests that LSG resolves or improves hyperlipidemia in morbidly obese patients. The aim of this study was to systematically review the effect of LSG on hyperlipidemia. Methods. A systematic literature search was conducted from Englishlanguage studies published from 2000 to 2012 for the following databases: MEDLINE, EMBASE, CINAHL, PubMed, Clinical evidence, Scopus, Dara, Web of Sciences, TRIP, Health Technology Database, Cochrane library, and PsycINFO. Results. A total of 4,211 articles were identified in the initial search, and 4,185 articles were excluded based on the exclusion criteria. Twenty-six studies met the inclusion criteria for this systematic review, involving 3,591 patients. The mean preoperative body mass index (BMI) was 48 ± 7.0 kg/m 2 (range 37.2-65.3). The mean postoperative BMI was 35 ± 5.9 kg/m 2 (range 26.3-49). The mean percentage of excess weight loss (EWL) was 63.1% (range 37.7-84.5), with a mean followup of 19.1 months (range 6-60). The mean levels of pre and post operative cholesterol were 194.4 ± 12.3 mg/dL (range 178-213) and 181 ± 16.3 mg/dL (range 158-200), respectively. Conclusion. Most patients with hyperlipidemia showed improvement or resolution of lipid profiles after LSG. Based on this systematic review, LSG has a significant effect on hyperlipidemia in the form of resolution or improvement in the majority of patients.

European Journal of Heart Failure Supplements, 2008

Physical Review Letters, 2004

We prepare a novel suspension composed of rodlike fd virus and thermosensitive polymer poly(N-iso... more We prepare a novel suspension composed of rodlike fd virus and thermosensitive polymer poly(N-isopropylacrylamide) whose phase diagram is temperature and concentration dependent. The system exhibits a rich variety of stable and metastable phases, and provides a unique opportunity to directly observe melting of lamellar phases and single lamellae. Typically, lamellar phases swell with increasing temperature before melting into the nematic phase. The highly swollen lamellae can be superheated as a result of topological nucleation barriers that slow the formation of the nematic phase.

Physical Review Letters, 2004

We report the creation of nematic nanotube gels containing large domains of isolated, oriented, h... more We report the creation of nematic nanotube gels containing large domains of isolated, oriented, half-micron-long, single-wall carbon nanotubes (SWNTs). We make them by homogeneously dispersing surfactant coated SWNTs at low concentration in an N-isopropyl acrylamide gel and then inducing a volume-compression transition. These gels exhibit hallmark properties of a nematic: birefrigence, anisotropy in optical absorption, and disclination defects. We also investigate the isotropic-to-nematic transition of these gels, and we describe the physical properties of their ensuing nematic state, including a novel buckling of sample walls. Finally, we provide a simple model to explain our observations.

Physical Review Letters, 2010

We study melting mechanisms in single and polycrystalline colloidal films composed of diametertun... more We study melting mechanisms in single and polycrystalline colloidal films composed of diametertunable microgel spheres with short-ranged repulsive interactions and confined between two glass walls. Thick films (>4 layers), thin-films ( 4 layers), and monolayers exhibit different melting behaviors. Thick films melt from grain boundaries in polycrystalline solid films and from film-wall interfaces in singlecrystal films; a liquid-solid coexistence regime is observed in thick films but vanishes at a critical thickness of 4 layers. Thin solid films (2 to 4 layers) melt into the liquid phase in one step from both grain boundaries and from within crystalline domains. Monolayers melt in two steps with a middle hexatic phase.

Physical Review E, 2008

Melting of two-dimensional colloidal crystals is studied by video microscopy. The samples were co... more Melting of two-dimensional colloidal crystals is studied by video microscopy. The samples were composed of microgel spheres whose diameters could be temperature tuned, and whose pair potentials were measured to be short ranged and repulsive. We observed two-step melting from the crystal to a hexatic phase and from the hexatic to the liquid phase as a function of the temperature-tunable volume fraction. The translational and orientational susceptibilities enabled us to definitively determine the phase transition points, avoiding ambiguities inherent in other analyses and resolving a "dislocation precursor stage" in the solid phase that some of the traditional analyses may incorrectly associate with the hexatic phase. A prefreezing stage of the liquid with ordered patches was also found.