Slow fluctuations in enhanced Raman scattering and surface roughness relaxation

We propose an explanation for the recently measured slow fluctuations and ``blinking'' in the surface enhanced Raman scattering (SERS) spectrum of single molecules adsorbed on a silver colloidal particle. We suggest that these fluctuations may be related to the dynamic relaxation of the surface roughness on the nanometer scale and show that there are two classes of roughness with qualitatively different dynamics. The predictions agree with measurements of surface roughness relaxation. Using a theoretical model for the kinetics of surface roughness relaxation in the presence of charges and optical electrical fields, we predict that the high-frequency electromagnetic field increases both the effective surface tension and the surface diffusion constant and thus accelerates the surface smoothing kinetics and time scale of the Raman fluctuations in manner that is linear with the laser power intensity, while the addition of salt retards the surface relaxation kinetics and increases the time scale of the fluctuations. These predictions are in qualitative agreement with the Raman experiments

Active-Duty Physicians' Perceptions and Satisfaction with Humanitarian Assistance and Disaster Relief Missions: Implications for the Field

BACKGROUND: The United States Department of Defense participates in more than 500 missions every year, including humanitarian assistance and disaster relief, as part of medical stability operations. This study assessed perceptions of active-duty physicians regarding these activities and related these findings to the retention and overall satisfaction of healthcare professionals. METHODS AND FINDINGS: An Internet-based survey was developed and validated. Of the 667 physicians who responded to the survey, 47% had participated in at least one mission. On a 7-point, Likert-type response scale, physicians reported favorable overall satisfaction with their participation in these missions (mean  = 5.74). Perceived benefit was greatest for the United States (mean  = 5.56) and self (mean  = 5.39) compared to the target population (mean  = 4.82). These perceptions were related to participants' intentions to extend their military medical service (total model R (2)  = .37), with the strongest predictors being perceived benefit to self (β = .21, p<.01), the U.S. (β = .19, p<.01), and satisfaction (β = .18, p<.05). In addition, Air Force physicians reported higher levels of satisfaction (mean  = 6.10) than either Army (mean  = 5.27, Cohen's d = 0.75, p<.001) or Navy (mean  = 5.60, Cohen's d  = 0.46, p<.01) physicians. CONCLUSIONS: Military physicians are largely satisfied with humanitarian missions, reporting the greatest benefit of such activities for themselves and the United States. Elucidation of factors that may increase the perceived benefit to the target populations is warranted. Satisfaction and perceived benefits of humanitarian missions were positively correlated with intentions to extend time in service. These findings could inform the larger humanitarian community as well as military medical practices for both recruiting and retaining medical professionals