Changes in Food Preference and Taste Responses after Roux-en-Y Gastric Bypass

Currently, the most powerful therapy for obesity is bariatric surgery both in terms of significant weight loss and long-term efficacy. Most surgeons regard the Roux-en-Y gastric bypass (gastric bypass) operation as “gold standard” for obesity treatment. However, underlying mechanisms by which gastric bypass induces and sustains weight loss are not fully understood, but include reduced hunger, increased satiety, increased energy expenditure, altered taste, as well as reduced preference for foods with a high fat and sugar content. In fact, gastric patients often report idiosyncratic changes in taste perception that involves “sweet” taste and a calorie-dense food. I herein aimed to investigate how gastric bypass reduces intake of and preference for food high in fat and sugar in rats and humans. I found that the proportion of dietary fat in gastric bypass patients was significantly reduced six years after surgery compared with patients after vertical-banded gastroplasty. In addition, gastric bypass patients had an increased sucrose detection sensitivity compared with before surgery and controls, but hedonic taste ratings of sucrose in bypass patients remained unchanged. Rats after gastric bypass exhibit a shift away from high to low fat food. When compared to sham-operated rats, gastric bypass rats did not prefer high sucrose and fat concentrations in a two bottle preference test, but preoperative sucrose exposure reduced this effect. There was no difference in appetitive or consumatory behaviour in the brief access test between the sham-operated and gastric bypass rats. An oral gavage of 1 ml corn oil in gastric bypass rats induced conditioned taste aversion which was also demonstrated after exogenous administration of the GLP-1 receptor agonist exendin-4 (2 μg/kg intraperitoneal) in unoperated rats. These findings suggest that an altered food preference may contribute to long-term maintained weight loss after gastric bypass. Postingestive effects resulting in conditioned taste aversion may partially explain this observation

Steady supersonic Navier-Stokes solutions of a 75 deg delta wing

Steady solutions about a slender sharp edged delta wing in a supersonic freestream for moderate and high angles of attack are obtained numerically by time integration of the unsteady compressible three dimensional laminar Navier-Stokes equations. The main features of the flow, including primary and secondary separation, and vortex position and strength, are adequately simulated in the numerical solutions. Improved resolution of the computational grid in the leading edge region from a previous solution had considerable effect on the accuracy of the solutions. Good agreement between numerical solutions and experimental data was obtained for two cases. A local timestepping procedure is used to speed convergence by approximately a factor of two

Force and moment measurements on a 74 deg delta wing with an apex flap

Results are presented of a subsonic experimental investigation of an apex flap concept on a 74 deg swept delta wing with trailing-edge flaps. The apex flap comprised approximately 6 percent of the wing area forward of a transverse hinge, allowing for upward and downward deflection angles from +40 deg to -20 deg. Upward deflection forces leading-edge vortex formation on the apex flap, resulting in an increased lift component on the apex area. The associated nose-up moment balances the nose-down moment due to trailing-edge flaps, resulting in sizeable increase in the trimmed lift coefficient particularly at low angles of attack. Nose-down apex deflection may be used to augment the pitch control for rapid recovery from high-alpha maneuvers. This report presents the balance data without analysis

Leading-edge receptivity to a vortical freestream disturbance: A numerical analysis

The receptivity to freestream vorticity of the boundary layer over a flat plate with an elliptic leading edge is investigated numerically. The flow is simulated by solving the incompressible Navier-Stokes system in general curvilinear coordinates with the vorticity and stream function as dependent variables. A finite-difference scheme which is second-order accurate in both space and time is used. As a first step, the steady basic-state solution is computed. Then a small amplitude vortical disturbance is introduced at the upstream boundary and the governing equations are solved time-accurately to evaluate the spatial and temporal growth of the perturbations leading to instability waves (Tollmien-Schlichting waves) inside the boundary layer. Preliminary results for a symmetric, 2-D disturbance reveal the presence of Tollmien-Schlichting waves aft of the flat-plate/ellipse juncture

Hyperconvexe puntverzamelingen

Der Begriff "uberkonvex" wurde in die Mathematik eingefuhrt von Herrn A. E. MAYER und zwar durch dessen in der "Mathematisehen Zeitsehrift" erschienenen Aufsatz: "Eine Ueberkonvexitat". Diese Arbeit hat mich zum Sehreiben meiner Dissertation veranlaszt. Zuvor gebe ich eine kurze Ubersicht der MAYERschen Arbeit. ... Zie: Einleitun