Giant resonant light forces in microspherical photonics

Resonant light pressure effects can open new degrees of freedom in optical manipulation with microparticles, but they have been traditionally considered as relatively subtle effects. Using a simplified two-dimensional model of surface electromagnetic waves evanescently coupled to whispering gallery modes (WGMs) in transparent circular cavities, we show that under resonant conditions the peaks of the optical forces can approach theoretical limits imposed by the momentum conservation law on totally absorbing particles. Experimentally, we proved the existence of strong peaks of the optical forces by studying the optical propulsion of dielectric microspheres along tapered microfibers. We observed giant optical propelling velocities ∼0.45 mm s−1 for some of the 15-20 µm polystyrene microspheres in water for guided powers limited at ∼43 mW. Such velocities exceed previous observations by more than an order of magnitude, thereby providing evidence for the strongly enhanced resonant optical forces. We analyzed the statistical properties of the velocity distribution function measured for slightly disordered (∼1% size variations) ensembles of microspheres with mean diameters varying from 3 to 20 µm. These results demonstrate a principal possibility of optical sorting of microspheres with the positions of WGM resonances overlapped at the wavelength of the laser source. They can be used as building blocks of the lossless coupled resonator optical waveguides and various integrated optoelectronics devices

Femtosecond optical transfection of individual mammalian cells

Laser-mediated gene transfection into mammalian cells has recently emerged as a powerful alternative to more traditional transfection techniques. In particular, the use of a femtosecond-pulsed laser operating in the near-infrared (NIR) region has been proven to provide single-cell selectivity, localized delivery, low toxicity and consistent performance. This approach can easily be integrated with advanced multimodal live-cell microscopy and micromanipulation techniques. The efficiency of this technique depends on an understanding by the user of both biology and physics. Therefore, in this protocol we discuss the subtleties that apply to both fields, including sample preparation, alignment and calibration of laser optics and their integration into a microscopy platform. The entire protocol takes similar to 5 d to complete, from the initial setup of the femtosecond optical transfection system to the final stage of fluorescence imaging to assay for successful expression of the gene of interest

Moving beyond the link between HRM and economic performance : a study on the individual reactions of HR managers and professionals to sustainable HRM

This study contributes to the growing literature on the intersection between human resource management and corporate sustainability (CS) and, in particular, on sustainable human resource management (interpreted here as HRM practices informed by the CS principles, thus aiming at economic, social, environmental and human sustainability simultaneously). In particular, this paper claims that the members of the HR professional community can increase their job satisfaction and decrease their intention to leave by implementing sustainable HRM. In addition, we test for the mediating role played by the meaning that HR professionals and managers attach to HR work. Indeed, when HR professionals and managers are involved in sustainable HRM perceive their job to become more meaningful as it has a broader scope which goes beyond the solely focus on economic performance, and that leads then to higher job satisfaction and lower turnover intention. The study, which is based on 176 questionnaires collected through a cross-country survey, has been developed in partnership between the authors and a leading European association of HR managers and professionals. Our findings, which in general extend the knowledge on the employees' perception of CS-employee attitudes relationships, represent a data-driven argument for a more active role of HRM in developing Sustainable HRM