Visualizing aerosol-particle injection for diffractive-imaging experiments

Delivering sub-micrometer particles to an intense x-ray focus is a crucial aspect of single-particle diffractive-imaging experiments at x-ray free-electron lasers. Enabling direct visualization of sub-micrometer aerosol particle streams without interfering with the operation of the particle injector can greatly improve the overall efficiency of single-particle imaging experiments by reducing the amount of time and sample consumed during measurements. We have developed in-situ non-destructive imaging diagnostics to aid real-time particle injector optimization and x-ray/particle-beam alignment, based on laser illumination schemes and fast imaging detectors. Our diagnostics are constructed to provide a non-invasive rapid feedback on injector performance during measurements, and have been demonstrated during diffraction measurements at the FLASH free-electron laser.Comment: 15 page

Influence of Polarisation on Optical Trapping Forces in Air-Transport of Spherical Particles

We show, both theoretically and experimentally, that light polarization affects the driving forces through the change in absorption, and thus the speed of transport of spherical particles in air with counter-propagating optical vortex beams

Movement for women´s rights of General Pico La Pampa

Desde la vuelta de la democracia en nuestro país, muchos movimientos sociales se gestaron con diferentes fines, entre ellos los que luchan por la defensa de los derechos de las mujeres. La provincia de La Pampa, no ha estado exenta de este fenómeno. En un período de más de tres décadas aparecieron en el escenario social pampeano diversos movimientos. Pero es sobre fines del siglo XX, que emergen varios otros cuyos objetivos son claramente feministas y están ligados a la defensa expresa de los derechos de las mujeres. Este es el caso del Movimiento por los Derechos de las Mujeres de General Pico, objeto de estudio en este trabajo. Ubicándome en una perspectiva regional y de género, la presente investigación es motorizada por los siguientes interrogantes: la constitución de este movimiento ¿implicó una re-significación y reconstrucción de las identidades, individuales y colectivas, de sus integrantes? ¿En qué sentido? ¿En qué contexto deciden agruparse? ¿Cuáles fueron o son sus objetivos? ¿Qué planes de acción tienen? ¿Han obtenido logros? ¿Cuáles?Since the return to democracy in our country, many different movements, having different aims appeared. Among them, those which would strug- gle for the defence of women’s rights. The province of La Pampa has not been exempt from this fenomenon. In a period of more than three decades flourished in the pampean social scenery several movements.Nontheless, it is about the end of the 20th century that many other emerged, whose objectives are clearly feminist, and they are bound to the express defence of women’s rights. This is the case of Movement for Women’s Rights of General Pico”, subject of study in this paper. Adopting a regional perspective, from a gender viewpoint, this research is powered by the following question- ings: Did the constitution of this movement implied a resignification and reconstruction of both, individual and collective identities of its mem- bers? In what sense? In which context do they decide to group? Which were, a still are their aims? Which lines of action do they have? Have they achieved any goals? Which ones?

Bessel Beam as Optical Injector of Particles for X-ray Morphology

We apply a high aspect-ratio first order Bessel beam, formed by imaging a vortex beam through an axicon, to guide biological macromolecules and viruses to the focus of femtosecond x- ray free-electron-laser for coherent diffractive imaging

Toward steering a jet of particles into an x-ray beam with optically induced forces

Optical trapping of light-absorbing particles in a gaseous environment is governed by a laser-induced photophoreticforce, which can be orders of magnitude stronger than the force of radiation pressure induced by the same lightintensity. In spite of many experimental studies, the exact theoretical background underlying the photophoreticforce and the prediction of its influence on the particle motion is still in its infancy. Here, we report the results of aquantitative analysis of the photophoretic force and the stiffness of trapping achieved by levitating graphite andcarbon-coated glass shells of calibrated sizes in an upright diverging hollow-core vortex beam, which we refer to asan ‘optical funnel’. The measurements of forces were conducted in air at various gas pressures in the range from 5mbar to 2 bar. The results of these measurements lay the foundation for developing a touch-free optical system forprecisely positioning sub-micrometer bioparticles at the focal spot of an x-ray free electron laser, which wouldsignificantly enhance the efficiency of studying nanoscale morphology of proteins and biomolecules in femtosecondcoherent diffractive imaging experiments

Optically Induced Forces Imposed in an Optical Funnel on a Stream of Particles in Air or Vacuum

Optical trapping of light-absorbing particles in a gaseous environment is governed by a laser-induced photophoretic force, which can be orders of magnitude stronger than the force of radiation-pressure induced by the same light intensity. In spite of many experimental studies, the exact theoretical background underlying the photophoretic force and the prediction of its influence on the particle motion is still in its infancy. Here, we report the results of a quantitative analysis of the photophoretic force and the stiffness of trapping achieved by levitating graphite and carbon-coated glass shells of calibrated sizes in an upright diverging hollow-core vortex beam, which we refer to as an ‘optical funnel’. The measurements of forces were conducted in air at various gas pressures in the range from 5 mbar to 2 bar. The results of these measurements lay the foundation for mapping the optically induced force to the intensity distribution in the trap. The mapping, in turn, provides the necessary information to model flight trajectories of particles of various sizes entering the beam at given initial speed and position relative to the beam axis. Finally, we determined the limits of the parameter space for the particle speed, size, and radial offset to the beam axis, all linked to the laser power and the particular laser beam structure. These results establish the grounds for developing a touch-free optical system for precisely positioning sub-micrometer bioparticles at the focal spot of an x-ray free electron laser, which would significantly enhance the efficiency of studying nanoscale morphology of proteins and biomolecules in femtosecond coherent diffractive imaging experiments