Irrigation in Africa and Asia - politics and problems

Irrigation in Africa and Asia - politics and problem

Detecting 20 nm Wide Defects in Large Area Nanopatterns Using Optical Interferometric Microscopy

Due to the diffraction limited resolution and the presence of speckle noise, visible laser light is generally thought to be impractical for finding deep subwavelength defects in patterned semiconductor wafers. Here, we report on a nondestructive low-noise interferometric imaging method capable of detecting nanoscale defects within a wide field of view using visible light. The method uses a common-path laser interferometer and a combination of digital image processing techniques to produce 70 μm by 27 μm panoramic phase and amplitude images of the test nanopattern. Significant noise reduction and high sensitivity are achieved, which enables successful detection of several different types of sparse defects with sizes on the order of 20 nm wide by 100 nm long by 110 nm tall

Measuring the Nonuniform Evaporation Dynamics of Sprayed Sessile Microdroplets with Quantitative Phase Imaging

We demonstrate real-time quantitative phase imaging as a new optical approach for measuring the evaporation dynamics of sessile microdroplets. Quantitative phase images of various droplets were captured during evaporation. The images enabled us to generate time-resolved three-dimensional topographic profiles of droplet shape with nanometer accuracy and, without any assumptions about droplet geometry, to directly measure important physical parameters that characterize surface wetting processes. Specifically, the time-dependent variation of the droplet height, volume, contact radius, contact angle distribution along the droplet’s perimeter, and mass flux density for two different surface preparations are reported. The studies clearly demonstrate three phases of evaporation reported previously: pinned, depinned, and drying modes; the studies also reveal instances of partial pinning. Finally, the apparatus is employed to investigate the cooperative evaporation of the sprayed droplets. We observe and explain the neighbor-induced reduction in evaporation rate, that is, as compared to predictions for isolated droplets. In the future, the new experimental methods should stimulate the exploration of colloidal particle dynamics on the gas–liquid–solid interface

Dissolution Chemistry and Biocompatibility of Single-Crystalline Silicon Nanomembranes and Associated Materials for Transient Electronics

Single-crystalline silicon nanomembranes (Si NMs) represent a critically important class of material for high-performance forms of electronics that are capable of complete, controlled dissolution when immersed in water and/or biofluids, sometimes referred to as a type of “transient” electronics. The results reported here include the kinetics of hydrolysis of Si NMs in biofluids and various aqueous solutions through a range of relevant pH values, ionic concentrations and temperatures, and dependence on dopant types and concentrations. <i>In vitro</i> and <i>in vivo</i> investigations of Si NMs and other transient electronic materials demonstrate biocompatibility and bioresorption, thereby suggesting potential for envisioned applications in active, biodegradable electronic implants