Effects of Postprandial Body Position on Gastrointestinal Motility, the Autonomic Nervous System and Subjective Comfort

We examined postprandial body positions’ effects on gastrointestinal motility, the autonomic nervous system and subjective comfort, i.e., whether lowering the head after a meal is beneficial for gastrointestinal motility and the prevention of pressure ulcer. We examined 10 healthy subjects and compared 3 body positions: (1) Seated upright. (2) Lying on a bed with the head at 60° and knees up by 20° (60° position). (3) Identical to (2) until post-meal; the head was then lowered to 30° (60°-30° position). Gastrointestinal motility was assessed as gastrointestinal sounds measured by sound-editing software. Digital plethysmography assessed autonomic nerve function as heart rate variability. The pressure ulcer risk was estimated as subjective comfort/discomfort using a visual analog scale. Gastrointestinal sounds increased post-meal. The 60°-30° position showed the highest number of sounds and longest cumulative sound duration. Post-meal, sympathetic activation was suggested in the 60° position, whereas vagal activity was relatively preserved in the 60°-30° position. The 60°-30° position was the most comfortable, and the 60° position was least comfortable. Lowering the head after a meal is beneficial to augment gastrointestinal motility and decrease the pressure ulcer risk. The 60° head-up position increases the pressure ulcer risk

Optical Trapping-Formed Colloidal Assembly with Horns Extended to the Outside of a Focus through Light Propagation

We report optical trapping and assembling of colloidal particles at a glass/solution interface with a tightly focused laser beam of high intensity. It is generally believed that the particles are gathered only in an irradiated area where optical force is exerted on the particles by laser beam. Here we demonstrate that, the propagation of trapping laser from the focus to the outside of the formed assembly leads to expansion of the assembly much larger than the irradiated area with sticking out rows of linearly aligned particles like horns. The shape of the assembly, its structure, and the number of horns can be controlled by laser polarization. Optical trapping study utilizing the light propagation will open a new avenue for assembling and crystallizing quantum dots, metal nanoparticles, molecular clusters, proteins, and DNA

Optical Trapping-Formed Colloidal Assembly with Horns Extended to the Outside of a Focus through Light Propagation

We report optical trapping and assembling of colloidal particles at a glass/solution interface with a tightly focused laser beam of high intensity. It is generally believed that the particles are gathered only in an irradiated area where optical force is exerted on the particles by laser beam. Here we demonstrate that, the propagation of trapping laser from the focus to the outside of the formed assembly leads to expansion of the assembly much larger than the irradiated area with sticking out rows of linearly aligned particles like horns. The shape of the assembly, its structure, and the number of horns can be controlled by laser polarization. Optical trapping study utilizing the light propagation will open a new avenue for assembling and crystallizing quantum dots, metal nanoparticles, molecular clusters, proteins, and DNA

Optical Trapping-Formed Colloidal Assembly with Horns Extended to the Outside of a Focus through Light Propagation

We report optical trapping and assembling of colloidal particles at a glass/solution interface with a tightly focused laser beam of high intensity. It is generally believed that the particles are gathered only in an irradiated area where optical force is exerted on the particles by laser beam. Here we demonstrate that, the propagation of trapping laser from the focus to the outside of the formed assembly leads to expansion of the assembly much larger than the irradiated area with sticking out rows of linearly aligned particles like horns. The shape of the assembly, its structure, and the number of horns can be controlled by laser polarization. Optical trapping study utilizing the light propagation will open a new avenue for assembling and crystallizing quantum dots, metal nanoparticles, molecular clusters, proteins, and DNA

Reflection Microspectroscopic Study of Laser Trapping Assembling of Polystyrene Nanoparticles at Air/Solution Interface

We present the formation of a single nanoparticle assembly with periodic array structure induced by laser trapping of 200 nm polystyrene nanoparticles at air/solution interface of the colloidal heavy water solution. Their trapping and assembling behavior is observed by monitoring transmission and backscattering images and measuring reflection spectra under a microscope. Upon the laser irradiation into the solution surface layer, nanoparticles are gathered at and around the focal spot, and eventually a nanoparticle assembly with the size much larger than the focal volume is formed. The assembly gives structural color in visible range under halogen lamp illumination, indicating that constituent nanoparticles are periodically arrayed. Reflection spectra of the assembly show a reflection band, and its peak position is gradually shifted to short wavelength and the bandwidth becomes narrow with time, depending on the distance from the focal spot. After the laser is switched off, red-shift is observed in the reflection band. These results indicate that nanoparticles are rearranged into a densely packed periodic array during laser irradiation and diffused out to the surrounding solution after turning off the laser. These dynamics are discussed from the viewpoints of the attractive optical trapping force and the electrostatic repulsive force among nanoparticles