Accurate Computation of Electric Field Enhancement Factors for Metallic Nanoparticles Using the Discrete Dipole Approximation

We model the response of nanoscale Ag prolate spheroids to an external uniform static electric field using simulations based on the discrete dipole approximation, in which the spheroid is represented as a collection of polarizable subunits. We compare the results of simulations that employ subunit polarizabilities derived from the Clausius–Mossotti relation with those of simulations that employ polarizabilities that include a local environmental correction for subunits near the spheroid’s surface [Rahmani et al. Opt Lett 27: 2118 (2002)]. The simulations that employ corrected polarizabilities give predictions in very good agreement with exact results obtained by solving Laplace’s equation. In contrast, simulations that employ uncorrected Clausius–Mossotti polarizabilities substantially underestimate the extent of the electric field “hot spot” near the spheroid’s sharp tip, and give predictions for the field enhancement factor near the tip that are 30 to 50% too small.     

Learning about violence against women in research methods: A comparison to traditional pedagogy.

The current study examined whether a community-engaged class in undergraduate psychology research methods was able to educate students about violence against women without sacrificing acquisition of research methods knowledge. We compared student outcomes in a traditional research methods course to those in a community-engaged research methods course. Students in the community-engaged course completed a research project on violence against women that was informed by the research needs of community partners. Drawing on pre- and post-assessments, we determined that students in both community-engaged and traditional courses showed significant increases in knowledge of research methods core concepts. In addition, students in the community-engaged course showed significant increases in knowledge about violence against women and beliefs about their ability to conduct engaged research in the future. Thus, the community-engaged course offered an opportunity to teach students about violence against women using engaged-learning practices without sacrificing acquisition of core research methods knowledge, relative to the comparison class. This study demonstrates that integrating trauma topics (in this case, violence against women) into the existing curriculum is a viable route to educating undergraduate students about trauma. Implications for incorporating trauma and community engagement into undergraduate curricula are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Self‐Assembled Large Au Nanoparticle Arrays with Regular Hot Spots for SERS

The cost‐effective self‐assembly of 80 nm Au nanoparticles (NPs) into large‐domain, hexagonally close‐packed arrays for high‐sensitivity and high‐fidelity surface‐enhanced Raman spectroscopy (SERS) is demonstrated. These arrays exhibit specific optical resonances due to strong interparticle coupling, which are well reproduced by finite‐difference time‐domain (FDTD) simulations. The gaps between NPs form a regular lattice of hot spots that enable a large amplification of both photoluminescence and Raman signals. At smaller wavelengths the hot spots are extended away from the minimum‐gap positions, which allows SERS of larger analytes that do not fit into small gaps. Using CdSe quantum dots (QDs) a 3–5 times larger photoluminescence enhancement than previously reported is experimentally demonstrated and an unambiguous estimate of the electromagnetic SERS enhancement factor of ≈10⁴ is obtained by direct scanning electron microscopy imaging of QDs responsible for the Raman signal. Much stronger enhancement of ≈10⁸ is obtained at larger wavelengths for benzenethiol molecules penetrating the NP gaps.     

Plasmonic Amplifiers: Engineering Giant Light Enhancements by Tuning Resonances in Multiscale Plasmonic Nanostructures

The unique ability of plasmonic nanostructures to guide, enhance, and manipulate subwavelength light offers multiple novel applications in chemical and biological sensing, imaging, and photonic microcircuitry. Here the reproducible, giant light amplification in multiscale plasmonic structures is demonstrated. These structures combine strongly coupled components of different dimensions and topologies that resonate at the same optical frequency. A light amplifier is constructed using a silver mirror carrying light‐enhancing surface plasmons, dielectric gratings forming distributed Bragg cavities on top of the mirror, and gold nanoparticle arrays self‐assembled into the grating grooves. By tuning the resonances of the individual components to the same frequency, multiple enhancement of the light intensity in the nanometer gaps between the particles is achieved. Using a monolayer of benzenethiol molecules on this structure, an average SERS enhancement factor <EF> ～10⁸ is obtained, and the maximum enhancement in the interparticle hot‐spots is ～3 × 10¹⁰, in good agreement with FDTD calculations. The high enhancement factor, large density of well‐ordered hot‐spots, and good fidelity of the SERS signal make this design a promising platform for quantitative SERS sensing, optical detection, efficient solid state lighting, advanced photovoltaics, and other emerging photonic applications.     

Special issue editorial: The art and science of trauma-focused training and education.

In spite of the importance of trauma education, efforts on the part of the Division 56 Education and Training Committee to identify higher education programs that emphasize trauma reveal surprisingly few programs (e.g., see http://www.apatraumadivision.org/ resources/apa_doctoral_sites.pdf). Lack of trauma education at undergraduate and graduate levels increases the urgency to develop effective training for postgraduate professionals. Compounding the problem of integrating effective trauma education and training at all stages of professional development, relatively little information about pedagogy is shared in our professional journals. This special issue addresses that gap by presenting articles focused on practices, theory, and data from a wide range of training/education settings (e.g., community clinics, VA settings, classrooms) focused on diverse forms of trauma exposure (e.g., disaster, military, child abuse/neglect, violence against women). The breadth of the topics and ideas conveyed in these articles reveals that we have many stakeholders whose interests lie in the development of high quality education and training practices, from higher education programs involving undergraduate and graduate students to practitioners seeking continuing education and managers/supervisors transforming health care delivery systems. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A serum-resistant cytofectin for cellular delivery of antisense oligodeoxynucleotides and plasmid DNA

Development of antisense technology has focused in part on creating improved methods for delivering oligodeoxynucleotides (ODNs) to cells. In this report, we describe a cationic lipid that, when formulated with the fusogenic lipid dioleoylphosphatidyliethanolamine, greatly improves the cellular uptake properties of antisense ODNs, as well as plasmid DNA. This lipid formulation, termed GS 2888 cytofectin, (i) efficiently transfects ODNs and plasmids into many cell types in the presence or absence of 10% serum in the medium, (ii) uses a 4- to 10-fold lower concentration of the agent as compared to the commercially available Lipofectin liposome, and (iii) is > or = 20-fold more effective at eliciting antisense effects in the presence of serum when compared to Lipofectin. Here we show antisense effects using GS 2888 cytofectin together with C-5 propynyl pyrimidine phosphorothioate ODNs in which we achieve inhibition of gene expression using low nanomolar concentrations of ODN. This agent expands the utility of antisense ODNs for their use in understanding gene function and offers the potential for its use in DNA delivery applications in vivo.