WAVELENGTH DEPENDENCE IN OPTICAL TWEEZERS

Optical trapping forces are dependent upon the difference between the trap wavelength and the extinction (scattering plus absorption) resonances of a trapped particle. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given experiment. Although optical forces due to a near-resonant laser beam have been extensively studied for atoms, the situation for larger particles has not been explored experimentally. The ability to selectively trap certain particles with a given extinction peak may have many practical applications. Here, resonance-based trapping is investigated using nanoshells, particles with a dielectric core and metallic coating that exhibit tunable plasmon resonances, and with silica and polystyrene beads. A measure of the trap strength was realized for single particles trapped in three dimensions, and near-resonant trapping was investigated by measuring the trap strength as a function of trap wavelength. Since the resulting trapping is highly temperature dependent, this necessitated temperature measurements of single optically trapped particles. To make these measurements a new optical tweezer apparatus was designed and constructed; the apparatus has wavelength tunability and was used to study these resonance effects. Optical trap stiffness, which is analogous to the spring constant of a stable trap, is measured for trapped particles that exhibit either single or multiple extinction resonances. The applications of this apparatus are not limited to force spectroscopy. Other measurement systems and techniques could be easily implemented into the custom-built apparatus, allowing for the measurement of various properties of single optically trapped particles as a function of wavelength

Tunable optical tweezers for wavelength-dependent measurements

Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them

Cultural Ambassadors: American Academics in the Soviet Union, 1958-1991

In response to the emerging Cold War conflict, American policymakers adopted cultural diplomacy as a permanent component of US foreign policy for the first time. In an attempt to win the hearts and minds of the worlds’ people, American leaders utilized international cultural outreach, through methods such as exchanges of students, teachers, and scientists, traveling exhibitions, radio and television broadcasts, publications, and tourism, among others. In recent decades, many historians have begun to explore the significance of these efforts. However, none of these works have examined the experience of those individuals who actually participated in the exchanges. This work begins to fill that void by focusing on American academics who travelled to the Soviet Union on educational exchange during the Cold War. By exploring their personal reports and recollections of their time behind the Iron Curtain, this study illuminates how they perceived their own nation, its values, and their own sense of national identity and purpose. Ultimately, I argue that these Americans used the image of the inferior Soviet “other” to cement a more unified national identity and affirm their feelings of American exceptionalism. Still, though their belief in American superiority remained constant throughout, their commitment to actively serve as America’s cultural representatives abroad waxed and waned at different points in the Cold War. Namely, although at the start of the program in 1958 exchangees enthusiastically assisted in spreading American values abroad, when American public opinion shifted against the Vietnam War their efforts immediately ceased. This shows specific examples of how conceptions of American ideology changed in this period. For a time, these Americans, and probably many others, abandoned a tenet that had long been central to American identity- the belief that the United States had the duty to assert its ideology globally. It was not until the last years of the Cold War, when American and Soviet leaders made significant improvements in superpower relations, that these individuals felt confident enough to serve again as cultural ambassadors. These fluctuations provide a case study of the direct and personal effects of major political and foreign policy shifts on ordinary Americans

The effects of a mindfulness-based lifestyle program for adults with Parkinson's disease:A mixed methods, wait list controlled randomised control study

BACKGROUND: Parkinson’s disease (PD) is the second commonest neurodegenerative disease in developed countries. Current treatment for PD is pharmacologically focused and can have significant side-effects. There is increasing interest in holistic approaches including mindfulness to help manage the challenges associated with living with PD. We hypothesised that there would be an improvement in PD associated function and wellbeing in participants after participating in a 6-week mindfulness-based lifestyle program, and that these improvements would be sustainable at 6 months. Our primary objective was to determine changes in function and wellbeing associated with PD. METHODS: An exploratory prospective, mixed-method, randomised control trial incorporating a before and after design with a waitlist control, with an embedded qualitative component was conducted in 2012–2013. Participants included community living adults with disability congruent to H&Y Stage 2 PD, aged 18–75, fluent in spoken and written English and able to attend at least four of six sessions of the program. Participants were randomised to the intervention or wait-list control groups at two locations. All participants in the wait-list control group eventually received the intervention. Two randomisation codes were created for each location. Allocation to the intervention or wait-list control was by random number generation. The program facilitator and participants were blinded to participant data. RESULTS: Group 1 included 35 participants and group 2 (the waitlist control), 37. Data was analysed from 24 (group 1) and 33 (group 2) participants. The intervention group, compared to the waitlist control, showed a small improvement in function and wellbeing associated with PD immediately after the program (t-score = −0.59) and at 6-month post intervention (t-score = −1.42) as reported by the PDQ-39 SI. However this finding was not significant (p = 0.56 and 0.16 respectively). A small yet significant effect size (β = 0.23) in PDQ-39 ADL was reported in group 1 after 6-months post-intervention. This showed a positive improvement in the ADL as reported by group 1 after 6-months (t-score −1.8, p = 0.04). Four secondary measures are reported. CONCLUSIONS: Our findings suggest mindfulness-based lifestyle programs have potential to assist participants in managing the ongoing difficulties associated with a neurological condition such as Parkinson’s disease. Importantly, our study shows promise for the long term benefits of such programs. Improvements to participant activities in daily living and mindfulness were retained at 6-months post intervention. A more definitive study should be conducted in a larger sample of PD patients to further explore these findings and their impact on reducing stress and anxiety in PD patients. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12612000440820, 17(th) April 2012