Effect of Aqueous HCl with Dissolved Chlorine on Certain Corrosion-Resistant Polymers.

Polypropylene, poly(ethylene terephthalate), ethylene chloro tetrafluoroethylene, ethylene tetrafluoroethylene, and epoxy vinyl ester resin (Derakane 470-300) were evaluated in aqueous HCl containing chlorine gas at high temperature as a corrosion media. Fourier transform infrared, X-ray diffraction, energy-dispersive X-ray, and dynamic mechanical analyzer are used for identification of nature of chemical reactions on polymer chain. Puncture resistance and hardness tests were done to evaluate the mechanical strength after the exposure. The scanning electron microscopy image was taken to check the morphological change of polymer surface. Chlorination and oxidation reactions were observed to be responsible for the stability behavior of polymer. A mechanism proposed for both chlorination and oxidation on polymer.

Detachment and reorientation of cells using near-infrared laser microbeam.

Reorientation of adhering cell(s) with respect to other cell(s) has not been yet possible, thus limiting study of controlled interaction between cells. Here, we report cell detachment upon irradiation with a focused near-infrared laser beam, and reorientation of adherent cells. The detached cell was transported along the axial direction by scattering force and trapped at a higher plane inside the media using the same laser beam by a gravito-optical trap. The trapped cell could then be repositioned by movement of the sample stage and reoriented by rotation of the astigmatic trapping beam. The height at which the cell was stably held was found to depend on the laser beam power. Viability of the detached and manipulated cell was found not to be compromised as confirmed by propidium iodide fluorescence exclusion assay. The reoriented cell was allowed to reattach to the substrate at a controlled distance and orientation with respect to other cells. Further, the cell was found to retain its shape even after multiple detachments and manipulation using the laser beam. This technique opens up new avenues for noncontact modification of cellular orientations that will enable study of intercellular interactions and design of engineered tissue.

Trapping and two-photon fluorescence excitation of microscopic objects using ultrafast single-fiber optical tweezers.

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample.