Discriminatory effects in the optical binding of chiral nanoparticles

The laser-induced intermolecular force that exists between two or more particles subjected to a moderately intense laser beam is termed ‘optical binding’. Completely distinct from the single-particle forces that give rise to optical trapping, the phenomenon of optical binding is a manifestation of the coupling between optically induced dipole moments in neutral particles. In conjunction with optical trapping, the optomechanical forces in optical binding afford means for the manipulation and fabrication of optically bound matter. The Casimir-Polder potential that is intrinsic to all matter can be overridden by the optical binding force in cases where the laser beam is of sufficient intensity. Chiral discrimination can arise when the laser input has a circular polarization, if the particles are themselves chiral. Then, it emerges that the interaction between particles with a particular handedness is responsive to the left- or right handedness of the light. The present analysis, which expands upon previous studies of chiral discrimination in optical binding, identifies a novel mechanism that others have previously overlooked, signifying that the discriminatory effect is much more prominent than originally thought. The new theory leads to results for freely-tumbling chiral particles subjected to circularly polarized light. Rigorous conditions are established for the energy shifts to be non-zero and display discriminatory effects with respect to the handedness of the incident beam. Detailed calculations indicate that the energy shift is larger than those previously reported by three orders of magnitude

Sculpting optical energy landscapes for multi-particle nanoscale assembly

To understand the forces and dynamics of two or more neutral particles trapped within an optical beam, careful consideration of the influence of inter-particle forces is required. The well-known, field-independent intrinsic force is known to derive from the Casimir-Polder interaction. However, the magnitude of this force may be over-ridden by the effect known as optical binding, in cases when the laser beam is of sufficient intensity. This binding interaction is completely independent of optomechanical effects relating to optical tweezers, and involves a stimulated (pairwise) forward-scattering process. Unlike the Casimir-Polder coupling, optical binding is not always an attractive force when both particles are in their ground state. Associated with optical binding are potential energy surfaces, which reveal intricate patterns of local minima – sets of positions in which one of the particles will sit at equilibrium (with the other notionally set at the origin). These optical energy landscapes, which can be illustrated by use of contour diagrams, have mostly been considered for systems in which spherical particles are optically bound. The effect of different particle shapes, for example tube-like structures, can also be explored. Moreover, although the theory of conventional optical binding generally assumes situations in which both particles reside in their ground states, new results arise when individual particles are excited to a higher electronic state. Although, in the experimentally most convenient structural configuration (for tumbling spherical particles), pairwise optical binding vanishes in the short-range region, novel effects can arise as a result of non-zero optical binding between three neighbouring particles

Passive laser irradiation as a tool for optical catalysis

The mechanisms of absorption, emission, and scattering of photons form the foundations of optical interactions between light and matter. In the vast majority of such interactions there is a significant interplay and energy exchange between the radiation field and the material components. In absorption for example, modes of the field are depopulated by photons whose energy is at resonance with a molecular transition producing excited material states. In all such optical phenomena, the initial state of the radiation field differs in mode occupation to its final state. However, certain optical processes can involve off-resonance laser beams that are unchanged on interaction with the material: the output light, after interaction, is identical to the laser input. Such off-resonance interactions include forward Rayleigh scattering, responsible for the wellknown gradient force in optical trapping, and the laser-induced intermolecular interaction commonly termed optical binding; in both processes, an intense beam delivers its effect without suffering change. It is possible for beams detuned from resonance to provide not only techniques for optomechanical and optical manipulation, but also to passively influence other important and functional interactions such as absorption from a resonant beam, or energy transfer. Such effects can be grouped under the banner of ‘optical catalysis’, since they can significantly influence resonant processes. Furthermore, off-resonance photonics affords a potential to impact on chemical interactions, as in the passive modification of rotational constants and phase transitions. To date, apart from optical manipulation, the potential applicability of passive photonics, particularly in the realm of chemical physics and materials science, has received little attention. Here we open up this field, highlighting the distinct and novel role that off-resonance laser beams and the ensuing photonics can play

Clearwing Moths Captured by Ultraviolet Light Traps in Southern Ohio (Lepidoptera: Sesiidae)

Trapping with ultraviolet light in mixed-oak forests of Lawrence and Vinton Counties, Ohio in 1995 and 1996 yielded 46 Synanthedon acerni and four Synanthedon arkansasensis, a clearwing moth record new for the state

Pitch Mass Borer, a New Clearwing Moth Record for Ohio (Lepidoptera: Sesiidae)

We report the Pitch Mass Borer clearwing moth, Synanthedon pini, from Vinton Furnace Experimental Forest, Dundas, Vinton County, Ohio, the first record for this state. A mature larva and two pupae were excised from resin masses of Scrub Pine, Pinus virginiana, a new host record, in early May 1999

New Host Records of Parasitic Hymenoptera in Clearwing Moths (Lepidoptera: Sesiidae)

Synanthedon pictipes is host for Dibrachus cavus; Podosesia aureocincta hosts Phaeogenes ater, Macrocentrus marginator, and Lissonota sp.; Podosesia syringae hosts Lissonota sp

Film Archives: a Decaying Visual History

The 20th century saw a movement from the Industrial Revolution to what we could call the Communication Revolution, and perhaps a newer revolution in the past 20 years, which we could characterise as the Information Revolution. The Communication Revolution began with the discovery of photography (and shortly thereafter cinema) at the end of the 19th century. The Lumière brothers in France, Edward Muybridge in England and Thomas Edison in America all explored the possibilities of moving and still images. Rapid expansion of technology and opportunity saw the rise of revolutionary cinema in Russia and the emergence of Hollywood, the beginnings of an industry that today engulfs our world with images

Finding the Zone: Beyond the Social Construction of Masculine Gender Identity

Socially aware mindfulness and group counseling with an urban high school football team focuses on self, moral, and masculine gender identity development and interpersonal mindfulness. Based on the book, Boyz 2 Buddhas: Counseling Urban High School Male Athletes in the Zone

Critical Integral Contemplative Education

Mindfulness programs in education proceed with little awareness of the cultural, social, political, and developmental context in which they operate. This chapter first argues that social critique is a valuable practice in its own right and can be useful toward developing more socially just and inclusive education mindfulness programs. It is critical of how mindfulness is practiced in schools to the extent it shares qualities of McMindfulness and reinforces neoliberal ideologies, policies, and practices. Without this critical awareness of contexts programs tend to promote individualistic solutions to social problems and inequities and thereby serve to maintain the status quo of social injustice. This chapter critically employs concepts from Integral Meta-theory with an emphasis on cultural meanings, optimal human development, and universal social justice. It describes important realms of everyday life that are ignored by mindfulness education programs. It offers directions toward a critical integral contemplative education that promotes individual, interpersonal, and social development